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Oral Melanomas in Dogs

Oral melanoma is the most common oral tumor in the dog accounting for 30-40% of all canine oral tumors. Most patients are presented to their veterinarian for several reasons that can include: a mass seen in the mouth, dropping food, pain, foul breath, blood-tinged saliva, blood-stained toys or food, facial swelling and decrease in appetite/weight loss. If any of these signs or symptoms are seen, the first step is bringing your pet to your veterinarian in Towson, Columbia or Annapolis for evaluation.

oral melanomas in dogs in towson, columbia and annapolis, md

Breeds with a higher risk of developing oral tumors include the Cocker spaniel, German shepherd, German shorthaired pointer, Golden retriever, Gordon setter, Miniature poodle, Chow chow and Boxer. Most melanomas are diagnosed in older dogs with the average age being 11 years of age.

Oral melanoma is an aggressive cancer that can metastasize (spread) in up to 80% of cases to the regional lymph nodes and lungs. These tumors are often pigmented, but there are some tumors that lack pigment (amelanotic). Due to the high metastatic potential, staging tests are recommended prior to definitive therapy since these tests can affect the patient’s outcome to treatment.

There are four different stages of melanoma. Dogs with stage I (<2 cm) and II (2-4 cm without lymph node or lung involvement) disease have a better long-term prognosis than dogs with stage III (4 cm or greater and/or lymph node metastasis) or stage IV (distant metastasis). The information below is broken into various categories to help you better understand the staging process, prognosis and treatment for patients with oral melanoma.

Diagnosis/Staging

A biopsy is recommended for any abnormal mass in the mouth to obtain a definitive diagnosis.

Some melanomas can be difficult to diagnose, and additional testing (known as special stains) may be necessary if the biopsy is inconclusive. These stains are performed on the original biopsy sample that was submitted to the laboratory and may take about two weeks for the final results.

Prior to beginning any treatment, staging is recommended.
This includes chest radiographs or CT scan of the chest (to look for evidence of lung metastasis), full blood work (CBC and chemistry panel, urinalysis), and aspiration of the regional lymph nodes +/-CT/MRI to assess the extent of the tumor. Other tests may be advised depending on the health of the patient.

Prognostic Factors:

Size of the tumor
<2 cm has a better prognosis than larger tumors

Location
Animals with rostral tumors (towards the front of the mouth) have a more favorable prognosis.

Animals with oral tumors in the middle or back of the mouth tend to have a poorer prognosis, which may be related to the difficulty in surgical removal.

Melanomas on the lip tend to have a more favorable prognosis compared to ones located on the gingival/oral mucosa.

Stage
Stage I: median survival time is 12-18 months
Stage II: median survival time of 5-8 months
Stage III: median survival time of 3 months

Treatmentdog outside

Treatment is divided into two sections: local control of the original tumor and systemic treatment due to the high potential for metastasis (spread to other sites).

Localized treatment

Surgery
The treatment of choice for local control is surgery since this is the best chance to remove the entire tumor. Some patients may need a CT scan performed prior to surgery to determine the extent of disease and to ensure that surgery is the most appropriate local treatment. The goal of surgery is to remove all of the mass with adequate margins and this may involve removing a portion of the bone of the upper or lower jaw. Fortunately, most dogs do very well with this surgery and their quality of life is not affected.

Radiation Therapy
Two forms:
Definitive therapy which is used in conjunction with surgery when the oral tumor is incompletely or narrowly excised in order to address the concern for tumor recurrence. Definitive therapy includes once or twice weekly treatments for 4-6 treatments. The goal of the radiation therapy is to help kill any residual disease that remains after surgery and decrease/slow the risk for recurrence.

Palliative therapy is performed when surgery is not an option or owners are not interested in aggressive surgery/treatment, but want to make their dog more comfortable. This involves once weekly treatments for 3-5 weeks in a row and there is minimal negative impact on the patient with this protocol. Fortunately, most melanomas are responsive to radiation therapy with 75% of patients experiencing a decrease in tumor size which can last 4-8 months depending on the stage of disease.

Systemic Therapy
Due to the high metastatic nature of these tumors, systemic therapy is also advised in addition to local therapy. Unfortunately, even when these tumors are controlled locally with surgery and/or radiation, most patients succumb to the disease because of metastasis to the lymph nodes and lungs as well as other organs. As a result, we encourage the use of the melanoma vaccine to try to combat the metastatic disease.

Canine melanoma vaccine (Oncept) is a xenogenic vaccine that is administered once every two weeks in the muscle of the inner thigh for 4 treatments. After the initial 4 doses, a booster vaccine is given once every 6 months thereafter. The vaccine is designed to stimulate the patient’s immune system to specifically target the melanoma cells. This vaccine is not known to have any systemic side effects, but rarely can cause some irritation at the injection site, a low-grade fever and depigmentation of fur or skin. The downside to the vaccine is that it can take a minimum of 2-3 months before the body’s immune system is stimulated enough to start targeting the melanoma cells for destruction.

This treatment can be used in combination with any of the local therapies listed above.

Chemotherapy is not commonly recommended because of the lack of efficacy. Chemotherapy has only been shown to be of benefit in less than 30% of patients and is usually reserved for patients with aggressive or fast-growing tumors in an attempt to slow them down in order to give the vaccine a chance to work.

Piroxicam is an oral non-steroidal anti-inflammatory medication that can help to stimulate the immune system. This is a non-steroidal anti-inflammatory that has been shown to have some activity against tumors by stimulating the immune system to attack cancer cells. This medication is administered at home on a daily basis. Side effects are uncommon, but can include vomiting, diarrhea, anorexia, and gastrointestinal ulcers. For most patients, these side effects may be avoided by giving the medication with food. Rare toxicity of the liver and kidneys can be noted, so periodic blood work is recommended to monitor for any adverse effects. Unfortunately, only 10-20% of patients will experience a benefit with piroxicam.

Goal

The ultimate goal of any treatment is to improve your pet’s quality of life and your veterinary oncologist will work with you to determine the treatment option that you feel most comfortable with.

Lymphoma in Cats

Lymphoma is one of the most common cancers diagnosed in cats. It is a cancer of the lymphocytes (a type of white blood cell) and is found throughout many areas of the body which include: lymph nodes, spleen, liver, gastrointestinal tract and bone marrow.

Unlike lymphoma in dogs, viral causes of feline lymphoma are well defined, and the feline leukemia virus (FeLV) has been shown to cause a significant (~60 fold) increase in risk for development of lymphoma in cats. We typically see lymphoma diagnosed in younger cats that are infected with the feline leukemia virus, and in older cats that are not infected with the virus. Other possible risk factors include exposure to second hand tobacco smoke, chronic immunosuppressive therapy, as well as chronic inflammatory diseases.

lymphoma in cats in towson, annapolis and columbia, md

Types of Lymphoma

Lymphoma can be subdivided into several different forms which is dependent on location of the tumor. These locations can include:

Gastrointestinal Tract: The most common form is involvement of the gastrointestinal (GI) tract. This includes the stomach, intestines and liver; as well as some of the lymph nodes surrounding the intestines. Cats with this type of lymphoma often have clinical signs consisting of vomiting, diarrhea, weight loss or a decreased appetite.

Mediastinal: The mediastinum is a term used for a special aggregation of lymphoid tissue in the chest. Cats with this type of lymphoma are usually young and often seen because of a sudden onsent of difficulty breathing, decreased energy level and decrease in appetite.

Renal: The kidneys can be the primary sites of involvement. Cats that have this type are often seen because of signs related to kidney failure (increased thirst, increased urination, loss of appetite, vomiting).

Bone Marrow: If the cancer were confined to the bone marrow, it is considered leukemia. Most patients are presented to the hospital for a decrease in energy and appetite. Bloodwork, usually reveals a change in their red blood cell and white blood cell counts.

External Lymph Nodes: In a few cats, the only site of involvement is the external lymph nodes. These cats may be seen because of problems such as vomiting and loss of appetite or because the owner found “lumps” (enlarged lymph nodes) on their cat.

Other Sites: We will occasionally see other sites such as the skin, nose, brain and spinal cord as the primary site of involvement

Diagnosis and Initial Evaluation

A biopsy (tissue) or cytology (aspirate) sample is required in order to make a diagnosis of lymphoma. In some cases, we can obtain a diagnosis by a fine needle aspirate, but in other situations, a biopsy to obtain a larger piece of tissue is necessary to confirm the diagnosis. The ease with which a diagnosis can be obtained depends upon where the tumor is located.

The first step for any patient suspected of having lymphoma includes determining the extent of the disease which is known as staging. This includes a complete blood count (CBC), serum chemistry profile (which looks at things such as liver and kidney function, protein levels, blood sugar and electrolytes), urinalysis and FeLV/FIV testing are always recommended and provide important information regarding the effects of the cancer on body functions as well as the ability of the patient to handle chemotherapy or other treatments. Additional tests include chest radiographs, abdominal ultrasound along with possible bone marrow aspirate and CT/MRI. Once we determine the extent of disease, we can then decide on the best treatment for your pet.

Treatment and Prognosis

Chemotherapy is the mainstay of treatment for lymphoma; however, there may be situations when surgery and/or radiation are also indicated. Radiation therapy may be recommended if the cancer is localized to one site such as the nasal cavity. Specific recommendations will be discussed based on your pet’s particular situation.

Fortunately, lymphoma is very responsive to chemotherapy where 50-70% of treated cats will go into remission. The definition of remission is the complete disappearance of detectable cancer; however, microscopic amounts of tumor cells can remain hidden in the body. A remission is NOT a cure but it does allow your pet to experience a good quality of life without clinical signs associated with their disease. The length of the remission depends upon many factors including the primary site, how your pet is at the time of diagnosis and the extent of disease. In most situations, the median remission and survival times (with chemotherapy) are between six to twelve months; with 25% of cats experiencing disease control for greater than one year and approximately 10-15% of cats living longer than two years.

Solitary lymphoma such as nasal is generally treated with radiation +/-chemotherapy. The radiation can be considered definitive with the intent for long term control or palliative for symptom relief in order to
Improve and/or maintain the patient’s quality with minimal negative impact. The prognosis for solitary lymphoma such as nasal lymphoma is generally better with many cats achieving local control for 1-1.5 years although there is still a concern that the cancer may spread within 3-6 months. If solitary lymphoma is treated with radiation and the cancer progresses down the road, then chemotherapy can be considered at that time.

The exact chemotherapeutic drugs and schedule will depend upon how aggressively the cancer is behaving, how sick your pet is at the start of treatment, any abnormalities in organ function (particularly kidneys and liver), and the goals of treatment. Chemotherapy is most effective when we used a combination protocol; therefore, most protocols generally consist of 4-6 different drugs. This is called a multi-drug protocol. Multi-drug protocols most commonly include Elpsar (L’asparaginase), Vincristine (Oncovin), Cytoxan (Cyclophsophamide), Adriamycin (Doxorubicin) and Prednisone. Initially, treatments are given more frequently (i.e. once weekly) and then, depending upon the response and protocol used, are gradually spread out and/or discontinued. Other options for therapy may consist of using a single chemotherapy drug (single agent therapy) at 3- week intervals, or palliative care which is simply designed to keep your pet comfortable at home for as long as possible. Bloodwork and/or X-rays/ultrasounds are generally repeated at regular specified intervals to monitor for side effects (such as a low white blood cell count) and to determine the your pet’s response to treatment.

Side effects

Fortunately, most cats tolerate chemotherapy very well and experience minimal side effects. Serious side effects are only seen in 5% of the patients which require outpatient care and less than 1% will require hospitalization or experience any life threatening side effects. If side effects are serious or intolerable, we can consider either lowering the dose of the offending drug or substituting a different drug. Side effects include nausea, vomiting and loss of appetite, diarrhea, extreme tiredness or rarely infection. Certain chemotherapy agents can affect organ function over time, so close monitoring with bloodwork is recommended. Cats do not lose their hair but may lose their whiskers and have a different texture to their fur secondary to chemotherapy.

Goal

The ultimate goal of any treatment is to improve your pet’s quality of life and your oncologist will work with you to determine the treatment option that you feel most comfortable with.

Thyroid Tumors in Dogs

Thyroid tumors comprise 1.2-3.8% of all tumors in dogs and the majority (about 90%) are found to be malignant (known as thyroid carcinoma or thyroid adenocarcinoma). Breeds that have a higher risk of developing this type of cancer include Beagles, Boxers and Golden Retrievers although any dog can develop a thyroid tumor. Most dogs with thyroid tumors are older (>10 years).

Clinical signs

The most common sign is the finding of a mass in the neck. In most cases, these tumors are present on only on one side of the neck (unilateral) but there is a small percentage of dogs who around found to have cancer in both thyroid glands (bilateral). If the mass grows large enough, it could cause clinical signs which may include coughing, difficulty breathing or swallowing and rarely swelling in the face.

The majority of these tumors are considered to be non-functional (this means that they are not producing any thyroid hormone). Some dogs with this type of cancer are actually hypothyroid (have low levels of thyroid hormone). If the tumor is producing thyroid hormone, dogs can have signs of hyperthyroidism, which can include drinking and urinating more, weight
loss, increased panting and restlessness.

Diagnosis/staging

A diagnosis of a thyroid tumor can be made either by a needle aspirate or biopsy. These tumors often have a very well developed blood supply which means that an incisional biopsy (only taking a small piece of the mass) can be challenging and is not recommended due to the high risk of bleeding.
Not only can thyroid tumors be locally aggressive and invade into surrounding tissues as it grows, but up to 35% of patients have evidence of metastasis at the time of diagnosis. The most common sites of metastasis include the local lymph nodes and lungs. To assess the extent of disease, staging tests are recommended and include:

  • Chest radiographs determine if there is any evidence of disease in the lungs.
  • Blood work is recommended and consists of a CBC (which checks the red and white blood cells and platelets), a chemistry panel to look at organ function, a urinalysis and a thyroid level.
  • If surgery is going to be considered, a CT scan of the neck (and possible the chest) may be recommended as the next step after staging to help determine whether or not surgery will be successful and look a little closer for any evidence of metastasis. CT image shows large thyroid tumor (arrows).

Treatments

Surgery

Surgery is the treatment of choice whenever possible. Removal of these tumors can be complicated given the well developed blood supply and the fact that these tumors surround vital structures such as the esophagus and trachea. Whether surgery alone is enough or if radiation therapy and chemotherapy will be needed following surgery depends on the size and invasiveness of the tumor as well as the final biopsy report. Size of the tumor and invasiveness are predictors of outcome. Smaller tumors that are freely movable carry a better prognosis than larger or fixed thyroid tumors.

Radiation therapy

There are two different ways that radiation therapy can be used. The decision about what type of radiation therapy would be best is based on a number of different factors and the radiation oncologists recommendations.

For those dogs where the tumor can be removed but there are still tumor cells that remain at the surgical site, full course radiation therapy may be recommended. This type of radiation therapy involves the use of 15-20 treatments which is administered Monday through Friday for 3-4 consecutive weeks.

For those dogs whose tumors cannot be removed, we can consider using full course radiation therapy as described above although our ability to control the tumor is not as good due to the larger amount of tumor that needs to be treated.

For dogs that have tumors that cannot be removed, we can also consider a modified schedule of radiation therapy called palliative radiation therapy. This is a less intensive course of radiation therapy with fewer side effects but the trade-off is that it is not expected to control tumors for as long. Rather the goal of palliative radiation therapy is to focus on the patient’s quality of life. This type of radiation therapy involves the use of 3-4 treatments of radiation therapy with treatments being given at weekly intervals (ie. once weekly for 3-4 consecutive weeks).

Chemotherapy

Chemotherapy is frequently recommended due to the potential for metastatic disease, however, the treatment outcome is difficult to predict. Chemotherapy is most often discussed for tumors that cannot be removed, tumors that are larger than 3 cm, and/or tumors where there is invasion into the blood vessels or evidence of metastasis. Dogs that already have spread to the lungs at the time of diagnosis may also benefit from
chemotherapy. Chemotherapy is typically not used alone but is most often combined with surgery and radiation therapy.

  • The most commonly used drugs for this type of cancer are Palladia, Adriamycin (doxorubicin) and Carboplatin.
  • Doxorubicin and carboplatin are administered intravenously as an outpatient once every 3 weeks for a total of 4-6 treatments when combined with surgery. Palladia is an oral chemotherapy agent that is administered at home. Fortunately, the risk for side effects from chemotherapy is low and can include stomach upset (decrease in appetite, nausea, vomiting, diarrhea and/or lethargy), decrease in white blood cell counts and possible thinning of fur coat. Less than 10% of patients will need to come in to the hospital for outpatient care due to chemotherapy side effects and less than 1% will require hospitalization or experience any life threatening side effects.
  • The goal of chemotherapy is to help improve your pets quality of life and we will work with you to achieve this goal.

Radioactive iodine

Radioactive iodine has been used for the treatment of thyroid tumors in dogs although it is not commonly used due to technical issues. There are currently only a few facilities in the USA that are able to treat dogs with radioactive iodine so patients need to travel to one of these facilities. In addition, due to the doses that are needed for treatment, patients may need to remain in isolation for several weeks following treatment which makes this type of a treatment less practical.

Prognosis/Outcome

The prognosis with treatment depends partly on the size of the tumor and whether or not the tumor is freely movable or is fixed to the underlying structures. The prognosis is also influenced by the rate of growth of the tumor as we sometimes see tumors that are very slow to progress even in advanced stages.

For tumors that are small and freely movable, the prognosis with surgery alone is considered to be good with a median survival time of 2 years.

Larger tumors that can still be removed by surgery may require radiation therapy and/or chemotherapy after surgery. The survival time of these patients may not be as long but in our experience, the median survival time is 18-24 months with combination treatment.

For tumors that cannot be removed, the recommended treatment would be radiation therapy (either full course or palliative radiation therapy) AND chemotherapy. Dogs that fall into this category can experience survival times of 6-12 months.

Thyroid carcinoma is not usually a cancer that is curable, but with treatment, can be controlled while maintaining your pet’s good quality of life. Your oncologist will be able to discuss the treatment options, prognosis and help guide you as to the most appropriate plan for your beloved family member.