Tumors of the anal sac are uncommon a represent a small percentage of all tumors in dogs (<1%). The most common malignant tumor of the perianal region is the anal sac (gland) carcinoma accounting for 16.5% of all perianal tumors. These tumors are locally invasive and metastasize early in the course of the disease. There does not appear to be a breed or sex predilection for this tumor and no consistent causative factors have been noted.

In many cases, these tumors are noted as an incidental finding on a routine rectal examination and can range in size from very small to very large before clinical signs occur. In dogs with clinical signs, perianal swelling, straining to defecate, licking the perianal region, and bleeding, were most commonly seen and resulted from a large anal sac tumor or severely enlarged regional lymph nodes pressing on the colon. In other cases, increased drinking and urination was noted as a result of high calcium in the blood. High blood calcium may be seen in some cases secondary to the cancer and is associated with a blood factor released by the tumor. High blood calcium can cause significant kidney damage in some cases. It has been shown that up to 25% of dogs with anal sac tumors will have elevated calcium levels in the blood.

A diagnostic workup for this cancer includes bloodwork (CBC, serum chemistry), chest radiographs, abdominal ultrasound, and in some cases aspirates of the tumor or regional lymph nodes (if enlarged). A definitive diagnosis is obtained either by aspirates or biopsy of the tumor. This workup will also stage the patient and help determine where the tumor may have spread. Metastasis is relatively common with this tumor and may be present in 50% or more of dogs.

Once a diagnosis has been obtained, therapy will be determined based upon the size of the tumor and ability of the surgeon to remove the tumor without complications. Surgery offers the only chance for long-term control (a cure is sometimes possible) and involves removing the anal sac and regional lymph nodes if enlarged. In cases where surgery is not complete or “narrow” and some residual cancer cells exist at the surgery site, then radiation therapy may offer good local control. Radiation therapy is directed at the scar and also the regional lymph nodes (sublumbar). Acute side effects of radiation therapy may be noted and result in colitis and rectal irritation. During this time period, an e-collar must be worn to prevent licking of the area. Despite the side effects, radiation therapy is the best post-op treatment option that may provide long-term local tumor control in dogs with residual cancer.

The complete benefits of chemotherapy for this cancer are uncertain, however, chemotherapy is added to most protocols due to high chance of this cancer spreading by the surgery is instituted. Invasion of the tumor cells into regional blood and lymphatic vessels may be noted on the biopsy and will increase the potential for tumor spread/metastasis. The most commonly used chemotherapy agents include mitoxantrone, adriamycin, carboplatin, and gemcitabine. Other agents used as part of a treatment protocol include NSAIDs such as Deramaxx, Rimadyl, or Piroxicam. These drugs have been shown to have anticancer effects by directly killing cancer cells, increasing their sensitivity to radiation therapy or chemotherapy, and by killing blood vessels that feed tumors.

In most cases all three types of therapy are used (surgery, radiation therapy, and chemotherapy) in the treatment of dogs with anal sac carcinoma. A recent study in which dogs were treated with surgery, radiation therapy and chemotherapy (mitoxantrone), found that half the dogs lived for >900 days.

Prognostic factors help us to determine the likely outcome of a patient. Previously identified factors associated with this tumor include:

• Dogs with high calcium levels have a poor prognosis (250 days vs 580 days)

• Dogs with lung metastasis have a poor prognosis (219 days vs 548 days)

• Dogs treated with surgery as part of therapy had a better prognosis than those without surgery (548 days vs 402 days)

• Dogs with large tumors (>1 inch) have a poor prognosis (292 days vs 584 days)

In cases in which the tumor cannot be removed with surgery (large, bulky tumors or cases with distant tumor spread), treatment with palliative radiation therapy and various types of chemotherapy can be implemented. This type of radiation therapy (+/-chemotherapy) involves administering weekly treatments and is designed to shrink the tumor or prevent it from growing while alleviating any clinical signs associated with the tumor (ex: difficulty in urination/defecation, increased calcium level) and is not intended to cure dogs of their cancer. In one study, 75% of the dogs treated experience improvement of their clinical signs, 43% experienced a reduction in the size of the tumor and ~ 30% had disease stabilization. The overall duration of response was 6-9 months and the overall survival time was 11 months. Factors that significantly affected survival were: lymph node metastasis (8 months), resolution of clinical signs post treatment (15 months), and cases that experienced complete or partial regression of the tumor (15 months).

Newer chemotherapy agents such as Palladia (Toceranib) may also be considered to incorporate into the treatment protocol for dogs with anal sac tumors. This newer chemo agent has shown efficacy in shrinking and/or stabilizing tumors. Additionally, it can be considered as a cross-over (“rescue”) chemo in cases where indicated.

Cancer of the urinary tract in dogs can affect the kidneys, ureters, urinary bladder, prostate, or urethra. In the urinary system, the bladder is affected with cancer most commonly. Compared to cancer in other locations in the body, bladder cancer is unusual, comprising 1-2% of all cancers in the dog.

The most common cancer of the dog urinary bladder is invasive transitional cell carcinoma (TCC) of intermediate to high grade. TCC is a malignant tumor that develops from the transitional epithelial cells that line the bladder. In dogs, this tumor invades into the deeper layers of the bladder wall including the bladder muscles. Canine TCC also has the ability to spread to lymph nodes and to other organs in the body (lung, liver, and other sites). TCC most frequently is found in the bladder, but can also develop in the kidneys, ureters, prostate, and urethra. It can also spread from the bladder into neighboring organs. As a side note: 80% of humans with bladder cancer have a lower grade, less invasive form of TCC, but dogs and cats rarely get this less aggressive form of the cancer.

The exact cause of TCC in an individual dog is usually not known. In general, canine TCC results from a combination of several factors including genetic predisposition and environmental factors. A genetic predisposition is suspected because TCC is more common in specific breeds of dogs, including Scottish Terriers (18 fold increased risk compared to other breeds), Shetland Sheepdogs (4 fold increased risk), Beagles (4 fold increased risk), West Highland White Terriers (3 fold increased risk), and Wire Hair Fox Terriers (3 fold increased risk). Environmental factors identified as risk factors in previous studies have included pesticides, insecticides, and certain dietary factors. The greatest cause of TCC in humans is smoking, but further study is needed to determine the extent to which second-hand smoke may contribute to TCC in dogs.

Blood in the urine and straining to urinate are the most frequent signs of TCC. Pet owners must realize, however, that a urinary tract infection will cause these same symptoms, so the symptoms alone do not necessarily mean their dog has TCC. Less commonly, dogs with TCC can have lameness due to the spread of the tumor into the bones or coughing due to spread into the lungs. To diagnose TCC requires a tissue biopsy. Several other types of growths in the bladder, bladder infection, bladder stones, or bladder inflammation can cause similar symptoms as those in dogs with TCC. Some of these other conditions can cause abnormal cells in the urine, which can be mistaken for TCC. Therefore, diagnosis of TCC requires a tissue biopsy. A tissue biopsy can be obtained by surgery, cystoscopy (insertion of a fiberoptic scope into the bladder and biopsy through the scope), or in some cases with a urinary catheter.

Once a diagnosis of TCC is made, it is important to determine the extent of the tumor, i.e. to perform “tumor staging”. Tumor staging is performed to determine the best way to treat the cancer, to provide some information regarding prognosis, and to establish a baseline tumor measurement in order to determine if treatment is successful. Tumor staging for TCC includes radiographs of the thorax to look for lung metastasis, radiographs and ultrasound of the abdomen to look for metastasis in the abdomen and to assess any changes in the kidneys that result from obstructed urine flow. This information is needed to best plan how to treat the cancer. Also, these tests can be repeated during treatment to know if the treatment is being effective. Approximately 20-30% of dogs have metastasis to “distant” sites such as the lungs, but up to ½ will have “regional” metastasis to the surgical site and nearby lymph nodes.

For dogs with TCC that has not spread beyond the bladder, surgical excision is recommended. In order to surgically excise the tumor, however, it needs to be located away from the neck of the bladder and the urethra. Several vital structures in the neck of the bladder (where these tumors commonly develop) make surgical excision in this location usually difficult, but multiple studies have found that even removing just part of the mass is beneficial for an improved outcome. It is not possible to remove a “margin” of normal tissue around these tumors, except in rare cases, thus microscopic tumor cells are left behind post-op and lead to cancer regrowth.

The vast majority of TCC cases are treated with medical therapy using two drugs: chemotherapy and non-steroidal anti-inflammatories (NSAIDs). Traditional chemotherapy agents include Mitoxantrone, Carboplatin, Adriamycin, Vinblastine, and others have been used in canine TCC. The response with chemotherapy alone has been rather disappointing with ~20% of dogs having remission. NSAIDs are also effective in ~20% of dogs, but combining chemotherapy with an NSAID will yield response rates of 40-50%. Commonly used NSAIDs include Deramaxx, Piroxicam, Metacam, and Rimadyl. The side effects of chemotherapy are usually tolerable in dogs. Information of specific medications can be discussed with the attending veterinarian.

It is not known how long dogs with TCC that are not treated will live. Survival is affected by the growth rate of the tumor, the exact location of the tumor within the bladder, and whether the tumor has spread to other organs or not. The median survival in dogs treated with chemotherapy or NSAIDs alone is 3-4 months. The median survival time improves to 6-8 months when these therapies are combined. The best prognosis occurs for dogs that have medical therapy following surgery. In patients where minimal tumor remains post-op and they are followed with chemo and NSAIDs, the median survival time increases to 1-1.5 years. If bulky tumor remains post-op, the median survival time is 10-12 months if the patients are followed with chemo and NSAIDs.

Dogs with TCC are very prone to developing a bacterial infection in the bladder. Therefore, frequent urinalysis, culture, and treatment with antibiotics may be necessary. A secondary bacterial infection can result in a sudden worsening in symptoms in dogs with TCC, and these dogs will improve with treatment with antibiotics.

Brain tumors are uncommonly diagnosed in dogs. The cause for brain tumors is unknown. Although a broad spectrum of tumor types has been reported in dogs, the two most commonly diagnosed primary tumors are gliomas, which tend to occur more commonly in short-nosed breeds, and meningiomas, which tend to occur in medium nosed breeds. Brain tumors can also represent spread from other sites (i.e. metastatic hemangiosarcoma or melanoma) or local extension into the brain in the case of nasal tumors, pituitary adenomas, and nerve sheath tumors. Although many primary tumors are histologically benign when examined under the microscope, the location confers a more malignant biologic behavior. Since the brain is contained within a fixed space, the presence of a tumor exerts secondary effects such as increased intracranial pressure, cerebral edema, or brain herniation, which are more clinically devastating than the tumor itself.

The most common clinical signs that dogs will present with are seizures, changes in behavior/attitude, circling, difficulty walking or even blindness and other deficits in the sensory organs. A neurologic examination will help localize the lesion to the central nervous system and should be followed with bloodwork to rule out other causes of seizures and altered mentation. X-rays of the skull are usually of little yield unless an extensive amount of bony changes have occurred. Computed tomography (CT) and MRI are the primary imaging modalities used to diagnose brain lesions. MRI is excellent to look at soft tissue changes while CT is better for examining bony lesions. Even though the major tumor types have been reported to have a “classic” appearance on advanced imaging techniques, a biopsy remains the sole means for making a definitive diagnosis. Once a mass is noted additional diagnostics that can be useful (depending on the given situation) are chest x-rays and an abdominal ultrasound to rule out spread to the brain from other sites (lungs, prostate) or a CSF tap in which a sample of fluid is removed from around the spinal cord and examined for the total amount of protein and white blood cells present. Some studies have shown that a normal white blood cell count and increased protein content in the CSF is more consistent with cancer but the results must be interpreted with caution, as this is not a 100% sensitive tool.

The primary goal of therapy for brain tumors is to improve or even eliminate when possible the adverse secondary effects and resulting clinical signs and include a combination of medical management, surgery, radiation therapy, and chemotherapy.

Medical management is often required to palliate clinical signs prior to diagnosis and definitive therapy. Steroids (prednisone) are often used to decrease surrounding tumoral inflammation and edema. Anti-convulsants such as Phenobarbital and potassium bromide are required in some dogs to control seizures. Depending on the individual patient, these drugs may be discontinued following definitive treatment.

Surgery has the advantage of removing the structural mass which immediately relieves intracranial pressure in addition to providing a tissue sample for a definitive diagnosis—however, surgery is not without risk and post-surgical complications include infection, edema, and hemorrhage. The location, size, and invasiveness of the tumor will determine the possibility for both surgical removal and completeness of surgical margins.

Radiation therapy (RT) can be used alone or in combination with other treatment modalities such as surgery and is well established for the treatment of intracranial neoplasms. The goal of RT is to destroy the tumor while preserving surrounding tissues which is optimized by the use of a radiation plan based on the results of the previously performed CT or MRI. Although numerous protocols have been reported in the literature to treat brain tumors, most protocols involve the use of small doses of radiation delivered daily for several weeks. This protocol appears to improve clinical signs with minimal late-term effects on normal tissues.

Chemotherapy may be employed depending on the tumor type. The type of blood vessels in the brain act as a “blood-brain barrier” and prevent entrance of toxic or foreign substances, including most chemotherapy drugs, into the CSF. Hydroxyurea, CCNU, and Cytosar are chemotherapeutic agents that can penetrate the blood-brain barrier and have been shown to improve clinical signs and reduce tumor size in some instances. The benefit of chemotherapy for dogs with incompletely excised brain tumors is currently unknown.

Overall prognosis is highly dependent on the therapy chosen. For dogs who receive only palliative medication (steroids and anti-convulsants) the median survival time is around 40-60 days, and the results from several studies have shown a significant improvement in survival time when surgery, radiation, and chemotherapy are used alone or in combination. Surgical excision alone improves the survival time to 4-6 months especially for those dogs whose tumor is considered to be completely removed with surgery.

Several reports in the veterinary literature have proven the efficacy of radiation therapy for canine and feline brain tumors. In dogs, the overall median survival time of dogs with brain tumors with or without prior surgery was approximately 18 or 12 months, respectively. Dogs who presented with severe neurologic signs did worse than those presenting with mild neurologic signs (6 months vs 21 months). Other important prognostic factors were:

Type of tumor (meningioma = better)

Size of tumor (<2cm3 = better)

Radiation as part of the protocol (better)

Primary vs Secondary tumor (primary = better)

The incidence of intestinal tumors in dogs is low in comparison to people. These tumors tend to occur in older dogs (>9 years) and signs vary from anorexia, vomiting, weight loss, lethargy to diarrhea, depending on the location of the tumor. Males and females tend to develop these tumors at equal rates, although there is a higher incidence of gastric (stomach) tumor formation in males than females. The most common gastrointestinal tumors in dogs are adenocarcinoma, leiomyosarcoma, and lymphosarcoma with, adenocarcinoma being the most common. Adenocarcinomas are often classified as infiltrative, expansile (sometimes with ulcer formation), polypoid, nodular/cobblestone, and annular based on the biopsy and gross appearance. A separate condition of benign polypoid adenoma formation sometimes affects the colon.

The initial staging consists of a CBC, serum chemistry, chest radiographs, and an abdominal ultrasound. This helps determine if the cancer has spread. Endoscopy is occasionally performed to determine the extent of the disease. Once the staging has been performed, we can determine the best treatment option, which includes some combination of surgery, chemotherapy, and non-steroidal anti-inflammatory drugs (NSAIDs), which are in the same class as aspirin and have been shown to have some anti-cancer effects. The use of NSAIDs alone can be curative for the benign polypoid condition. Like aspirin, other NSAIDs can damage the lining of the stomach over time in sensitive individuals or affect the kidneys so these organs are monitored with bloodwork while the dog is receiving this medication.

The above listed workup for gastrointestinal adenocarcinoma helps determine the extent of the tumor and if the cancer has spread. Unfortunately, with adenocarcinomas, some patients present with advanced disease, meaning it has already spread to other areas of the body such as the lymph nodes, mesentery (abdominal connective tissue), liver and/or lungs.

The main method of treatment for these tumors is surgical resection. It has been shown that patients having complete tumor removal will do substantially better than those without. With adenocarcinomas, surgery is generally followed with chemotherapy using a drug called Adriamycin (Doxorubicin) +/- Cytoxan, or in some cases, Carboplatin.

Based upon the results of surgery and the staging, we can offer some idea of prognosis. Although there is not a great deal of information in the veterinary literature with this cancer, extrapolating from human medicine, there are some factors that we use. They include histologic type of cancer, the spread of cancer to the lymph nodes or other areas of the body, development of abdominal fluid with circulating cancer cells, incomplete tumor removal with surgery, or extension of the tumor to the outer layer/surface of the intestine. Loco-regional metastasis to the lymph nodes is common (up to 70-80% chance) followed by the liver and lungs later in the course of the disease. Metastasis portends a poor prognosis, and the risk of metastasis increases with the tumor grade.

The overall prognosis depends on the tumor type, grade, and location. For instance, dogs with gastric tumors have an average prognosis of 6 months following surgery. Dogs with small intestinal tumors have an average prognosis of 10 months following surgery. The survival time of dogs with colon tumors has been associated with the appearance of the tumor, with survival times of 36 months, 12 months, and 1.6 months noted for pedunculated masses, nodular/cobblestone masses, and annular ring masses, respectively. Other factors such as diffuse disease/inability to completely excise the tumor, mitotic rate/tumor grade (aggressiveness of the tumor), presence of metastasis, and invasion into the vascular or lymphatic system suggest a shortened overall survival. If the tumor spreads to the lymph nodes, 50% of patients will not survive beyond 6 months, although the survival time should improve with chemotherapy.

In general, surgery remains the cornerstone of effective therapy for gastrointestinal tumors in dogs. The benefits of chemotherapy are unknown, but in many cases the expected survival times may increase 2-3 times beyond that of which are expected with surgery alone.

Canine histiocytic proliferative disorders include a wide spectrum of diseases characterized by different biologic behaviors. The causes for development of these diseases are largely unknown but suspected to be due to genetic abnormalities. Two of the more common forms we encounter are a benign and a malignant form. Both tend to occur in similar breeds including, Rottweilers, Bernese Mountain Dogs, and retrievers. The malignant form can be further subdivided into a localized histiocytic sarcomas arising from a single site (lymph node, skin, spleen, liver, lung, etc), and a disseminated form that involves many tissues such as lymph node, spleen, lung, brain, nasal cavity, and bone marrow. The localized form may disseminate (or metastasize).

Dogs may present with a variety of clinical signs depending upon whether the tumor is localized or disseminated. In the disseminated form, dogs are often clinically ill as a result of the cancer. They often present with low red blood cells, white blood cells and platelets as a result of the cancer infiltrating the bone marrow. Diagnosis is based upon aspiration or biopsy of the affected tissue. Therapy will depend in part on the animal’s clinical presentation as they may need supportive care in the form of a blood or plasma transfusion and the form of histiocytic sarcoma encountered. The localized form can be treated with surgery depending upon the site and followed up with chemotherapy (CCNU, Cytoxan, Adriamycin) and radiation if needed. The prognosis for the localized can be good depending upon the site. The disseminated form is treated with chemotherapy and carries a poor prognosis.

More recently, a chemotherapy drug called CCNU has been shown to have efficacy against this cancer and approximately 50-60% of dogs will respond to treatment. The most recent data found that the dogs that responded to treatment and had good prognostic factors had good cancer control for some time. Prognostic factors included: low albumin – a blood protein (poor), low platelets (poor), and spleen involvement (poor). CCNU is an oral chemotherapy agent that is given once every three weeks. With this drug, bloodwork (CBC) is drawn prior to chemotherapy and one week after. This drug may affect the white blood cells so the bloodwork one week after therapy is essential. If given many times this drug may affect the liver so blood chemistry values are monitored to ensure no liver damage occurs.

With effective therapy using chemo alone, 50% of dogs survive beyond 4 months. With effective chemotherapy and surgery, 50% of dogs survive beyond 1 year.

Infiltrative lipomas (tumors arising from fat cells, which are also called adipocytes) are uncommon in dogs and cats with limited information available in the veterinary literature. Simple lipomas are benign, well encapsulated, and can often be cured with surgery. However, infiltrative lipomas are very locally invasive and have a high tendency to recur following surgery but do not tend to metastasize (spread to other parts of the body). The infiltrative nature of these tumors means that the tumor invades deep tissue structures such as muscle, nerves, and bone, which is why surgical removal is difficult and sometimes impossible.

Dogs with infiltrative lipomas are staged with bloodwork, chest x-rays, and sometimes a CT or MRI depending on the location of the tumor. In cases of an operable tumor, it is recommended that a surgery is performed first to debulk the mass. Due to the locally invasive nature of this tumor, it is unlikely that surgery alone will be curative (except in certain cases were an aggressive surgery such as an amputation could be performed). The literature shows that surgery alone results in a recurrence rate of ~40% and half of the dogs experience tumor recurrence within 8 months. The dogs treated with surgery alone lived roughly 18 months.

Consequently, it is recommended to follow gross/marginal surgical removal of a tumor with radiation therapy post-op to maximize the chances of shrinking any remaining tumor and preventing it from recurring. In one study, 50% of dogs who received surgery (gross tumor removal) and radiation therapy survived longer than 40 months. Radiation can be administered to bulky tumor but is most effective for minimal disease. Chemotherapy is not typically warranted for these tumors due to the limited metastatic potential of this tumor type. In some cases, however, low dose therapy designed to prevent blood vessel development may be used in attempt to prevent tumor recurrence by limited blood supply to the tumor cells.

Primary hepatobiliary tumors (tumors of the liver and bile ducts) are rare in dogs, accounting for less than 2% of all canine neoplasms. They most often occur in older animals with no breed or sex predilection. Most neoplasms are malignant and no causative agents have been identified, however, the detoxification role of the liver may make the hepatobiliary system more susceptible to carcinogenic compounds. Hepatobiliary tumors are divided into one of four types: hepatocellular tumors, bile duct tumors, neuroendocrine tumors (carcinoids), and primary sarcomas. Hepatobiliary tumors have a moderate to high metastatic potential depending on the type (20-60% for hepatocellular carcinoma, 80% for biliary carcinomas, and 90% for carcinoids). However, low-grade tumors metastasize in <20-25% even though the multifocal disease may be present for hepatocellular carcinoma. Metastasis most commonly affects the regional lymph nodes, lungs, and the lining of the abdominal cavity.

Most dogs will present with clinical signs of liver disease at the time of diagnosis (anorexia, increased thirst/urination, vomiting, lethargy) and a mass or fluid is often noted on abdominal palpation. Full staging should be performed including bloodwork, which may reveal elevated liver enzymes, increased bile acids, clotting abnormalities, and/or a low blood glucose (studies have shown that as many as 38% of dogs may be hypoglycemic secondary to a hepatobiliary tumor). Chest radiographs should be performed to look for lung metastasis and abdominal radiographs and ultrasound should be performed to characterize the involvement and guide therapy (surgical resection for localized disease vs. chemotherapy for widespread involvement). An ultrasound-guided aspirate can also be obtained to differentiate between the different types of hepatobiliary tumors but a biopsy may be necessary for a definitive diagnosis. At the time of diagnosis, the tumor can be diffuse (diffusely present throughout all liver lobes), nodular (several nodules in multiple liver lobes), or massive (a large mass confined to one liver lobe). Advanced imaging techniques such as MRI have been shown to provide additional diagnostic information regarding benign vs. malignant lesions and to document widespread metastasis that may not be noted on ultrasound.

Hepatocellular tumors are most often hepatocellular carcinoma (HCC), which represents ~50% of all liver tumors. The benign version, hepatocellular adenoma is less common. Most dogs with HCC will present with a large mass confined to one liver lobe, making surgical resection the treatment of choice. Although there are few studies in the veterinary literature on this tumor, the median survival time with surgery alone is roughly 1.5 years. This means that 50% of the dogs lived longer and 50% lived shorter. Many oncologists will recommend follow-up chemotherapy due to the metastatic potential of this tumor. Recently there has been some investigation into using metronomic chemo for narrowly or incompletely removed HCC. Metronomic chemo is designed to be anti-angiogenic, or against new blood vessel formation. Cancer cells must acquire new blood vessels for oxygenation and nourishment in order to grow into a sizable mass. The goal of starting metronomic chemo is to prevent these blood vessels from forming to feed any microscopic cancer cells. This may thereby delay disease recurrence and improve the long-term prognosis. Metronomic chemo may be used for multifocal tumors, although typically standard chemo would be used in these cases.

Bile duct tumors are most often biliary carcinomas (BC), representing 20-40% of malignant liver tumors, followed by biliary adenomas. Biliary carcinomas can occur within the body of the liver or within the bile ducts and gallbladder and can be nodular or diffuse at the time of diagnosis. Unfortunately, the invasive nature of this tumor makes surgical resection difficult if not impossible and systemic chemotherapy is often not rewarding.

Carcinoids are almost always diffuse and highly metastatic. They are rarely able to be surgically removed unless it is a rare case that has a solitary mass. Chemo is generally poorly effective in treating these tumor types since they tend to be resistant to most chemo agents, however, treatment with newer chemo drugs such as Palladia (off-label) have shown promising results in anecdotal reports. Primary hepatic sarcomas are uncommon and are most commonly hemangiosarcoma or leiomyosarcoma. Hemangiosarcoma is an aggressive neoplasm originating from blood vessels. Metastasis (to the lungs or other intra-abdominal sites) is already present in a majority of cases at the time of diagnosis. Surgical resection of the primary tumor (when possible) and systemic chemotherapy is recommended.

One newer investigational form of therapy for localized, inoperable hepatic tumors is the used of chemoembolization. This is a process whereby a catheter is fed directly to the affected liver lobe and chemotherapy is deposited followed by a “blocking” agent to essentially cause that lobe to become dormant. This may prevent further progression of cancer outside of this lobe.

Primary lung tumors are relatively uncommon in dogs and account for only 1% of all tumors in this species. There has been a potential association with dogs developing lung tumors in a household of people who smoke as a result of second-hand smoke inhalation. The most common history of dogs with lung tumors is to present with coughing or exercise intolerance that may have been present for a relatively long time. Sometimes dogs have no clinical signs and the tumor is simply noted on routine radiographs.

Tumors are definitively diagnosed through a fine needle aspirate or through biopsy, which often involves removal of a lung lobe. The most common types of lung tumors are adenocarcinomas (bronchogenic or alveolar). Other types include squamous cell carcinoma, anaplastic and undifferentiated carcinoma, and rarely a sarcoma. These tumors can spread to nearby lymph nodes and then to other lung lobes or spread via the creation of a malignant pleural effusion (fluid in the chest with cancer cells noted in it). Rarely this type of cancer can cause lameness and swelling of legs due to inflammation of the bones caused by cancer in the chest. Routine blood work is always performed but not usually diagnostic for the cancer itself.

Treatment is via surgical removal of the affected lung lobe. At that time, any lymph nodes in the area are examined and aspirated if needed. Chemotherapy is often used when dogs have any poor prognostic indicators and if the cancer appears to have spread, or residual cancer is left in the chest. Many chemotherapy agents have been used, however, to date, no specific studies on which protocol is best is available. Generally, when chemotherapy is used the protocol depends upon the clinician’s experience. Recently, similar protocols to those used in human oncology have been used these include the use of Carboplatin and Vinorelbine. Additionally, there has been a great deal of interest in the use of nonsteroidal anti-inflammatory agents (NSAIDs) that have been shown to have anticancer effects against a variety of tumors in dogs.

Prognosis is dependent upon the presence of several indicators including:

1. Size (< 2 inches is good)

2. Metastasis (poor)

3. Malignant effusion (poor)

4. Tumor adhered to the chest wall (poor)

5. Squamous cell carcinoma (poor)

6. Undifferentiated tumors (poor)

7. Tumor in the periphery (good) vs central (poor)

8. Clinical signs at presentation (poor)

9. High-grade tumor (poor) vs low grade (good)

Generally, studies have shown that the overall survival time is greater than a year. Dogs with mostly good prognostic factors typically survive 1.5 years or longer, whereas those with negative prognostic factors have an average survival time of 6-10 months.

Mast cell tumors are common skin tumors in dogs. They account for 20-25% of all skin tumors in dogs. They are a cancer of mast cells, which are cells important in regulating inflammation and immune responses. The tumors may occur in dogs that have a history of allergic skin disease. About 50% occur along the trunk and perineum, 40% along the extremities and 10% along the head and neck. They can occur as a solitary lesion or be multiple. They can be haired, ulcerated, pedunculated, etc., and because of their different appearances are often called the “great imitator”. In most cases, dogs have a history of the mass being present and changing in size over time.

With mast cell tumors, several factors have been shown to be prognostic:

1. Grade: Low-grade tumors (Grade I) do better than high grade (Grade III).

2. Clinical stage: Tumors spread throughout the body carry a worse prognosis.

3. Location: Tumors along the perineum, gums, and oral cavity carry a worse prognosis.

   1. Systemic signs: Animals that are sick due to systemic disease often do worse.

   2. Completeness of surgery to remove the tumor: complete removal better.

4. Mitotic index: greater than 5 carries correlated to survival times of 2 months.

Various grading schemes exist for grading mast cell tumors, with the most commonly accepted scale being a 3-tiered scheme. Our recommendation for most cases is as follows with respect to the grade:

If grade I or II and the surgery was complete (all cancer removed) then the dogs are simply followed over time. With a complete surgery, up to 90-100% may never recur again. If surgery is incomplete we recommend a second surgery. If this is not possible due to location then we recommend radiation therapy (mast cell tumors are very responsive to radiation therapy and local control of 90% has been noted) for the tumor. If radiation therapy is declined, chemotherapy could be considered to prevent tumor recurrence, although it is not a direct substitute for adequate surgical control and/or radiation therapy. More recent studies have shown that there is a subset of grade II tumors that behave more aggressively. It is recommended that all grade II tumors are evaluated with special stains (proliferation markers and genetic analysis) to tease these out. If a high-grade II tumor is identified, then these dogs are treated with chemotherapy.

If a grade III tumor is found and completely removed, we still recommend follow up chemotherapy because of the aggressive nature of this tumor and high potential for metastasis. With surgery alone, the median survival (50% alive) is 6 months. With surgery followed by chemotherapy, the median survival increases to 12 months. In case of incompletely excised grade III tumors, we recommend either a second surgery or radiation therapy. One study found that dogs with incompletely excised grade III mast cell tumors followed by radiation therapy had a median survival of 20 months. It is our belief that with chemotherapy, these dogs would likely do even better. However, large tumors (>2 inches) and tumors with high-grade features may still only carry average survival times of 6 months depending on other prognostic factors. Typically combining surgery with radiation therapy and chemotherapy improves the prognosis.

In cases where the tumor cannot be removed due to size or location we typically offer palliative radiation therapy and chemotherapy. This particular protocol involved 4 weekly doses of radiation followed by a 15-week course of chemotherapy and is intended for patients that cannot be cured as it offers improvement in clinical signs and reduction in the size of the tumor. A recent study evaluated 65 dogs treated in this manner and found that 42% of the tumors responded (completely or partially reduced in size) and an additional 30% had stabilization of their disease. Nearly half of these dogs had cancer spread and were treated after failing other traditional therapies which explains the relatively short duration of response (2 months) and overall survival time (3 months). Factors that significantly affected outcome were: grade of the tumor (grade III did worse), location of the tumor (mucosal tumors experienced remission duration of 5 months and an overall survival of 7 months), and if chemotherapy was continued after radiation therapy (survival of 3.5 months vs 3 weeks if it was not). Although the survival time reported in this study is poor, palliative radiation therapy and chemotherapy can be offered for cases in which there is no other treatment option.

Palladia is a new drug and has become the first canine anti-cancer therapy approved by the FDA in the United States to treat mast cell tumors. The generic name is Toceranib Phosphate and this agent is the first of its class in veterinary medicine. Unlike traditional chemotherapy, Palladia is a more “targeted” chemotherapy agent. The target molecules for this particular drug are VEGFR, PDGFR, and c-kit, all proteins involved in cell growth and survival. Specifically, Palladia is labeled for use in mast cell tumors, which over-express c-kit in up to 50% of tumors.

In a clinical trial of dogs with mast cell tumors, Palladia helped nearly 70% of dogs to destroy, reduce, or halt the growth of tumors. In certain mast cell tumors, Palladia can “turn off” the abnormal protein signal (c-kit) that often plays a role in their growth and development. Interestingly, the drug has also been shown to reduce/slow the growth of other types of cancer by decreasing a tumors blood supply (by inhibiting both VEGFR and PDGFR) and limiting its nutrients.

Palladia is an oral anticancer medication given on an every other day basis at home. Although Palladia is oral and “targeted” in nature, severe side effects can occur if early signs are not detected. The most significant side effects may be GI in nature and include vomiting, nausea, diarrhea, loss of appetite, and weight loss. Additional side effects include neutropenia, anemia, and muscle cramping. If caught early and treated aggressively, most side effects are reversible depending on the patient’s clinical status.

Osteosarcoma (OSA) is the most common bone tumor in dogs accounting for nearly 85% of all bone tumors. There are two forms of OSA: 1) the appendicular form which occurs in the limbs and 2) the axial form which occurs within the skull, ribs, and pelvis. The incidence of this cancer in dogs is about 1:10,000. OSA most commonly occurs in large, middle-aged dogs weighing more than 40 pounds. The most common breeds include Saint Bernard, Great Dane, Golden Retriever, Labrador retriever, and Rottweiler. The appendicular form of OSA typically occurs near the wrist, shoulder, or knee. The cause of this cancer is unknown but based upon common breeds, there appears to be a genetic component. Other proposed causes include microscopic injury to bones in young growing dogs, metallic implants, and trauma.

The most common history associated with this cancer includes lameness that is nonresponsive to anti-inflammatory medications. On physical exam, swelling is often noted along the affected limb. Radiographs of the lesion aid in determining whether a bone tumor exists and destruction of the bone is usually noted. However, this does not diagnose a tumor. Diagnosis can only be accomplished via a bone biopsy or aspirate. As part of staging for this cancer, radiographs of the chest are taken. In 85% of dogs, the chest radiographs are normal indicating no obvious signs of spread (metastasis). In over 90% of dogs with appendicular OSA, metastasis is likely present but is too small to be visualized with radiographs. Computed tomography (CT), commonly used to scan the lungs in people, has been used in veterinary medicine and appears more sensitive in detecting metastasis in dogs than radiographs. The chance for metastasis for tumors in the axial location is <50%, therefore radiographs at generally sufficient for staging without the need for a CT scan of the lungs. Routine blood work (CBC and serum chemistry) is also performed in order to ensure favorable overall health of the patient prior to surgery as well as evaluate the enzyme alkaline phosphatase (ALP) which has been shown to be prognostic for this cancer.

Prognostic factors for this tumor include:

Dogs with large tumors (poor)

Dogs with visible cancer spread (poor)

Dogs with high ALP (poor)

Dogs receiving chemotherapy (good)

Older or very young dogs (poor)

Tumor location/metastasis (tumors on the limbs have a high rate of metastasis)

Anatomic tumor location (tumors arising from the ribs have a more aggressive behavior)

Tumor removal (non removal or incomplete removal is poor)

As far as treatment for this cancer, surgery is the mainstay of therapy for OSA and provides immediate relief of pain associated with this cancer. Prior to surgery, an orthopedic exam is necessary to ensure the patient has no concurrent orthopedic disease that would prevent an amputation if the tumor is appendicular. However, due to the aggressive nature of this cancer, surgery alone provides little long-term control. With surgery as a sole therapy for appendicular OSA, studies have shown that dogs develop cancer spread within 3-4 months and <10% of dogs will live 1 year. This is due to the fact that most dogs have micrometastatic disease at the time of presentation that proliferates once the primary tumor has been removed. Because of this, chemotherapy is recommended post-op. If the tumor is axial, the need to consider chemotherapy is contingent on the tumor grade and completeness of surgical removal. Chemotherapy is designed to kill cells that are rapidly growing such as the metastatic disease and residual disease at the tumor site. Radiation therapy is also used to treat incompletely excised axial tumors and is generally more effective at effectively treating the residual cancer cells at the surgery site.

Several chemotherapy agents have been used, including Adriamycin, Cisplatin and Carboplatin, as all appear to have similar efficacy against this tumor. Combination protocols utilizing these agents are designed to limit drug resistance by virtue of alternating between more than one drugs. However, studies have shown mixed results and it appears that the best combination protocol is not known; therefore, the current “gold-standard” is to administer 6 doses of Carboplatin single-agent therapy. With the addition of chemotherapy, studies show >50% of dogs will live one year or longer when treating the appendicular form of OSA. For rib OSA, 50% of dogs survive 8 months with surgery and chemo. The important point is that dogs maintain an excellent quality of life during therapy. For axial (skull and backbone) OSA the average survival time is 4-5 months, although in cases where the tumors affect the upper jaw, prognosis may be far better (1+ years with aggressive therapy). For OSA occurring in the soft tissues outside of the bone, the average survival time is 1-3 months, but this typically doubles when chemotherapy is used in conjunction with surgery.

In patients where surgery is not possible and pain relief is needed, radiation therapy may offer palliation, which is relief of bone pain without curing, in 80% of patients. This involves 4 treatments (1 x/week) of radiation therapy with minimal side effects. However, activity must be moderately restricted because the decrease of bone pain from the radiation therapy could cause most dogs to attempt to increase their activity, which could potentially lead to breaking the bone where the tumor is present. When palliative radiation therapy is given, chemotherapy may be given concurrently and has been shown to yield survival times around 6-8 months for 50% of the dogs; without chemo, survival time is generally around 4-5 months.

There are additional treatments that may be used in conjunction with surgery, radiation therapy, and chemotherapy. Non-steroidal anti-inflammatory drugs (NSAIDs), such as deramaxx, rimadyl, or feldene, have been shown to have anticancer effects against some types of carcinomas; however, limited data exists on the use of these drugs in treating thyroid tumors. Also, starting dogs on low-dose thyroid supplementation may be beneficial. A newer form of therapy that combines an NSAID with low-dose chemo is known as metronomic therapy. This form of treatment is designed to be anti-angiogenic, or against new blood vessel formation. Cancer cells must acquire new blood vessels for oxygenation and nourishment in order to grow into a sizable mass. The goal of starting metronomic chemo is to prevent these blood vessels from forming to feed any microscopic cancer cells. This may thereby delay disease recurrence and improve the long-term prognosis.

Pheochromocytoma is a special type of endocrine tumor that arises from the adrenal gland. The cells that give rise to this specific tumor secrete certain hormones that regulate various functions within the body. Tumors typically occur in middle-aged to older dogs. Many cases may have the tumors diagnosed incidentally, but up to half of the dogs have signs/symptoms present. These signs and symptoms include appetite loss, weight loss, panting, lethargy, collapse, elevated heart rate and high blood pressure.

Many of the tumors are locally invasive into regional tissue and surrounding blood vessels. Sometimes the tumors rupture a lead to pale gums, abdominal distention, and collapse. Tumor spread (metastasis) occurs in 20-30% of dogs. Tumors may be detected with abdominal ultrasound or other imaging modalities, but a biopsy is necessary to achieve a diagnosis.

Treatment largely centers around surgery to remove the tumor. In cases where the entire tumor cannot be removed, post-op chemotherapy is recommended. Unfortunately, pheochromocytomas are poorly responsive to traditional chemotherapy agents due to resistance mechanisms inherently present within the cells. The use of newer chemo agents such as Palladia and Kinavet may be considered as these types of chemotherapeutics may overcome certain types of drug resistance. Other forms of therapy include low dose treatment (metronomic therapy) designed to prevent blood vessel growth and tumor enlargement. Chemo and metronomic therapy have limited statistical information regarding the outcome.

The prognosis is variable and often predicted based on the local tumor aggressiveness, ability to surgically remove the tumor, and malignant features that may or may not be present on biopsy. In the cases where tumors are non-invasive and complete surgical removal is possible, the survival time is generally years and some patients may be considered ‘cured’ following surgery. In other cases, surgery will reduce the signs/symptoms associated with the tumor (see above) and provide a better quality of life for a patient. If the tumors are invasive, ruptured, high grade or advanced, or inoperable, the prognosis is more guarded and the survival time may only be a few months.

Plasmacytomas are solitary collections of cancerous plasma cells. Normal plasma cells are immune system cells that are responsible for the production of many different types of antibodies that fight infection. The proliferation of cancerous plasma cells results in a population of plasma cell clones that may produce a high number of one specific types of antibody in the blood (monoclonal gammopathy). Plasmacytomas can originate in bone or soft tissue and are referred to as solitary osseous plasmacytoma (SOP) or extramedullary plasmacytoma (EMP). When a diagnosis of any plasmacytoma has been made, the patient should be staged, making sure that it is confined to a single location in the body.

Extramedullary plasmacytoma (EMP)

EMPs are typically classified according to location: cutaneous/oral and noncutaneous. Cutaneous plasmacytoma is a tumor of older dogs with German Shepherds being somewhat over-represented. Tumors can cover the trunk, limbs, head (especially the ears), and oral cavity. For the most part, canine cutaneous plasmacytomas are benign, carrying an excellent prognosis following complete surgical excision. In a study of dogs with plasmacytomas involving a large number of cases, <4% recurred following surgical excision, <2% spread to other sites, and only 1% of dogs developed a systemic condition called multiple myeloma (see below). Radiation therapy is effective for cases in which surgical resection is not an option due to tumor size or location. Chemotherapy has been successful in cases where spread to other locations occurred. The biologic behavior of noncutaneous EMP tends to be more aggressive. Tumors have been reported to occur in the esophagus, stomach, and small and large intestines. Metastasis to the regional lymph nodes is common, warranting chemotherapy. The prognosis for plasmacytomas in the cat is unknown due to the paucity of information available on this tumor in the veterinary literature concerning felines.

Solitary osseous plasmacytoma (SOP)

SOPs can affect virtually any bone in the body. Local therapy is the treatment of choice once adequate staging has been performed to rule out systemic involvement. Surgical intervention is warranted in any case where the tumor has resulted in an unstable long-bone fracture or neurologic complications from spinal compression from an SOP in the spinal column. Surgical removal alone or in combination with radiation therapy has been successful in the local control of SOPs. Unfortunately, most patients with an SOP at the time of diagnosis will go on to develop a systemic disease, called multiple myeloma. Multiple myelomas is a systemic proliferation of plasma cells that typically involves multiple sites in the bone marrow and other organs. The plasma cells may cause an elevation in protein levels known as a monoclonal gammopathy—an overabundance of a single antibody that circulates in the blood and can spill into the urine. Given this information, there is some controversy in veterinary medicine as to whether chemotherapy should be initiated at the time of diagnosis of an SOP. Extrapolating from what we know in human medicine, adding chemotherapy at initial diagnosis provides no significant survival advantage. Unless the tumor is high grade, careful follow up is generally recommended to closely monitor blood work, radiographs, and the clinical symptoms of the patient.

There are two common types of skin lymphoma in dogs: epitheliotropic and non-epitheliotropic.

Epitheliotropic lymphoma is a cancer of immune system cells (lymphocytes). In this case, the cancer is born of lymphocytes residing in the skin (or other superficial sites such as the lips and oral cavity) thus it is generally localized. This disease is similar to mycosis fungoides in people. Most dogs will present with one of the following clinical presentations: a diffuse redness of the skin, plaque-like lesions, scaling, ulcerations or nodules in the skin, oral ulcerations, or involvement at the lip margins. The lesions can be distributed diffusely over the body or be localized to an area of the body. A suspicion of this type of cancer is based upon aspiration but is definitively based on biopsy.

By definition, this is a T cell lymphoma of the skin characterized by the presence of malignant cells surrounding hair follicles and sweat glands on the biopsy and is confined to the epidermis. The epitheliotropic form generally does not spread to other areas of the body until the disease becomes very widespread. Some dogs will present with enlarged lymph nodes at the time of diagnosis. In rare cases, blood involvement can occur (circulating cancerous cells in the blood).

Therapy for this type of cancer in most cases involves chemotherapy. The protocol uses CCNU as the primary agent and Prednisone as the main therapy. CCNU is an oral drug given once every three weeks. Bloodwork is recommended the week after therapy and prior to each cycle. If given many times, this drug can affect the liver thus a liver panel is examined periodically during treatment. Most dogs will respond well to this therapy and remissions are common for several months.

Novel treatments are on the horizon, and immunotherapy in the form of monoclonal antibody treatments is now available for dogs with lymphoma. These may improve the prognosis beyond that achieved with traditional therapy alone.

Since this is not a common form of lymphoma, there is not a great deal of information in the veterinary literature about this type of lymphoma. In a recent study, approximately 88% of dogs will have either a complete response or a partial response (50-100% improvement in skin lesions). The response generally lasts several months in most dogs. In dogs that fail this protocol, full weekly chemotherapy is initiated. In some isolated cases where a single solitary lesion exists, complete surgical removal can be curative. Another option for solitary lesions is radiation therapy. One additional systemic option with treatment is placing dogs on a vitamin A derivative (isotretinoin, or Accutane). This type of therapy may be effective at helping to induce a remission in many cases.

Non-epitheliotropic lymphoma is the least common form of cutaneous lymphoma in the dog. This type of cutaneous lymphoma may be of either B or T cell origin and manifest in the same manner as its epitheliotropic counterpart, although oral involvement is rare and formation of mass lesions is more common. In addition, most dogs will present with systemic involvement as the progression of skin lesions is rapid into the lymph nodes and other organs. Unfortunately, this type of lymphoma is poorly responsive to chemotherapy and remissions may be short. Full weekly chemotherapy is recommended using a combination of chemo drugs. Overall survival times are short, usually 4 months from onset of skin lesions unless a complete remission is reached, which improves the average survival to approximately 1 year.

Spindle cell sarcomas are also known as soft tissue sarcomas (STS) and in general, this term acts as an umbrella for a variety of tumors including (fibrosarcoma-connective tissue, chondrosarcoma-cartilage, liposarcoma-fat tissue, hemangiosarcoma-blood vessel cells, nerve sheath tumor, hemangiopericytoma-cells supporting blood vessels, malignant fibrous histiocytoma). These tumors range in their behavior based upon their cell of origin (see above) as well as their grade, which correlates to the aggressiveness of the tumor. Most tend to be low to moderate grade but exceptions exist. These tumors often grow slowly and grow passively along tissue planes. The rate of metastasis (spread to other organs) depends on the grade of the tumor with low and intermediate grade tumors metastasizing in <20% of dogs whereas high-grade tumors metastasize in 40-50% of dogs.

STS are often first noted as a lump by the owners that often grow slowly over time. Most often the mass feels fixed to the underlying tissue and its borders are indistinct. The best description of these tumors is an “octopus” in which the head of the octopus is the area of the tumor you can feel but the tumor has tentacles (tendrils) that can go much deeper (up to 2 inches) out into the surrounding normal tissue. The tendrils of the tumor are actually microscopic cells that are the most active part of the tumor and lead to re-growth when not surgically removed. Patients are staged with chest x-rays, blood work (CBC, serum chemistry), and abdominal ultrasound (if necessary). These tests allow us to determine if the cancer has spread to other areas in the body, which is dependent on the type/grade of the tumor.

Treatment for STS involves surgery that may be incomplete because of the local microscopic invasiveness; however, in cases where a tumor is on a limb, surgery can be curative with an amputation. In cases where the tumor is incompletely removed, we will often recommend either a second surgery (if feasible) or radiation therapy. Studies have shown that following up with radiation therapy can provide excellent local control (the majority of dogs have survival beyond 4-5 years). In cases where a tumor is a high grade or it is the type of tumor that has a great chance to spread, we often recommend chemotherapy in addition to the local therapy. Most often this entails adriamycin (IV) given once every 3 weeks for 5 treatments. At the end of the chemotherapy, dogs are restaged and continuously monitored for local recurrence. Dogs diagnosed with high-grade tumors have an average prognosis of 1.5 years due to the more aggressive features associated with these tumors.

STS that occurs in the oral cavity (mouth) tend to be more aggressive with higher rates of local recurrence. Treatment for these tumors often involves bone removal and minor reconstructive surgery followed by radiation. With aggressive therapy, 50% of dogs remain tumor-free 1.5-2 years later. STS that occurs internally on organs (liver, spleen, etc), tend to be more aggressive, high-grade tumors with a rate of metastasis that is approximately 50%. Removal of the tumors, when possible, is performed and these cases are almost always followed with chemotherapy. The average survival time is 6-12 months following the appropriate therapy.

Palliative therapy can be used in lieu of aggressive/curative-intent treatment options in cases where the tumor is not considered to be operable. These treatment options include radiation therapy, chemotherapy, medical therapy with metronomic chemotherapy (see below), and pain medications as deemed necessary. Approximately 1/3 of dogs have a favorable response to therapy and 1/3 of dogs will have tumor stabilization. The average survival time for patients treated with solely palliative therapy is typically between 6 months but mostly based on the presenting circumstances and response to therapy.

Metronomic therapy is sometimes used in addition to the “standard therapy” and consists of giving an NSAID (such as Deramaxx or Rimadyl) along with a low daily dose of a chemotherapy drug called Cytoxan. This type of therapy is administered orally and is designed to kill the growing blood vessels that feed tumors. Tumors produce growth factors that cause the growth of nearby blood vessels (angiogenesis) which then feed the tumor cells. These blood vessels are sensitive to chemotherapy at very low dosages. A recent study evaluated metronomic chemotherapy to delay soft tissue sarcoma recurrence if the tumors are incompletely removed. The study successfully demonstrated that dogs treated with metronomic chemotherapy had a significantly longer disease-free interval than dogs that did not receive chemotherapy (albeit this is only one study and not considered to be the “gold-standard”). In this series of patients, it was found that incompletely excised tumors recurred following surgery alone in close to 100% of the cases. The average time to recurrence is 8-9 months. The use of metronomic chemo for its immunomodulatory and anti-angiogenic effects delayed recurrence to close to 1.5 years and not all tumors will recur with this type of therapy. To learn more, call us today at (516) 501-1700.

Melanoma is a common tumor in dogs and may occur in the mouth, skin, toes, and eyes. These tumors commonly occur in Poodles, Dachshunds, Scottish terriers, Golden retrievers, Schnauzers, and Rottweilers. The behavior of the tumor depends on the location and grade.

Subungual (nail bed) melanoma is uncommon in dogs but represents one of the more frequently identified nail bed disorders. Subungual melanoma may metastasis in approximately 1/3 to 1/2 of dogs, and the regional lymph nodes and lungs are the most commonly affected sites. Surgical removal of the tumor requires amputation of the affected nail, and only a small percentage of tumors will recur locally at the surgery site post-op.

Treatment consists of surgery to remove the primary tumor followed by immunotherapy. Surgery is the mainstay of treatment but surgery alone has been shown to not completely cure all dogs in that many develop metastatic disease within several months post-op. Because of this we often follow up with immunotherapy (vaccination) to prevent and kill any systemic spread of cancer. In cases where the tumor was not completely removed radiation therapy can kill residual disease at the initial site of surgery. This helps to provide good local control, but dogs still need to be followed with immunotherapy because of the aggressive nature of this cancer.

Recently a DNA-based vaccine has been approved by the USDA to treat canine melanoma. The vaccine is administered into the muscle of dogs by using an air-compressed system which contains a gene for human tyrosinase (which codes for protein specific to melanoma cells). The protein made by the human gene is considered “foreign” and the dog’s immune system recognizes it as such and mounts an immune response against it. The vaccine, therefore, allows a dog’s own immune system to recognize melanoma cells as foreign and will mount a response against the melanoma cancer cells. Studies have noted excellent responses in dogs with their survival extended by years in many cases. What we have found is that the vaccine works best when there is complete local control with all residual local tumor removed by either surgery or radiation therapy. The vaccine involves 4 treatments on an every other week basis with a booster every 6 months.

The prognosis for subungual melanoma is cautiously optimistic. Survival can be measured in years for dogs treated aggressively that have not experienced metastasis of the cancer.

Thyroid tumors are uncommon tumors in dogs accounting for about 1-3% of all tumors. They often occur in middle-aged dogs and no sex predilection has been found. The breeds commonly seen with this cancer include Boxers, Golden Retrievers, and Beagles, but it has been found in a number of other breeds. The cause of this tumor is unknown, but there has been an increase in tumor formation after exposure to radiation therapy in nearby areas. Additionally, hypothyroidism is a risk factor in forming these tumors.

The common presentation for most dogs is the palpation of a mass in the area of the neck. The mass may be tightly adhered to the underlying tissue or freely movable. Some dogs may have coughing problems or swallowing difficulty. Some dogs may have signs of hyperthyroidism, which means their tumor is functional and secreting thyroid hormone. This is very rare though (<10%) and most cases have a nonfunctional tumor.

Staging for this cancer involves the following: routine bloodwork (CBC, serum chemistry), thyroid levels, chest radiographs, lymph node aspiration and tumor aspiration or biopsy. Factors that have been shown to play in role in how well dogs will do include: size of the tumor, histologic cell type, evidence of metastasis, and the amount of new blood vessels growing into the tumor. Therapy is based on several factors: size of the tumor, spread of tumor, the presence of disease in other organs and whether the tumor is functional or not.

Surgery to remove the entire tumor is a viable option when the tumor is small and freely movable. Studies have shown dogs can have survival times of over 2-3 years with surgery alone. If surgery is complete, meaning the entire tumor is removed, many dogs can simply be watched or continued with chemotherapy for high grade and invasive tumors. If surgical removal is narrow to incomplete, we recommend radiation therapy to remove any residual cancer. Chemotherapy could also be used as an alternative to radiation therapy, although may be slightly less effective at preventing local tumor recurrence. In cases where the tumor is too large to remove, many dogs will do very well with radiation therapy. Radiation therapy in these circumstances has yielded survival times of > 3 years for over 60-70% of the cases depending on the grade and stage of the tumor. Metastasis is a negative prognostic factor.

There are additional treatments that may be used in conjunction with surgery, radiation therapy, and chemotherapy. Non-steroidal anti-inflammatory drugs (NSAIDs) have been shown to have anticancer effects against some types of carcinomas. Also, starting dogs on low-dose thyroid supplementation may be beneficial. A newer form of therapy that combines an NSAID with low-dose chemo is known as metronomic therapy. This form of treatment is designed to be anti-angiogenic, or against new blood vessel formation. Cancer cells must acquire new blood vessels for oxygenation and nourishment in order to grow into a sizable mass. The goal of starting metronomic chemo is to prevent these blood vessels from forming to feed any microscopic cancer cells. This may thereby delay disease recurrence and improve the long-term prognosis.