Diagnosis and Treatment

Robyn Elmslie, DVM, DACVIM (Oncology)
Phyllis Glawe, DVM, MS, DACVIM (Oncology)

Quick Facts at a Glance:

• Lymphoma accounts for one-third of all malignancies in cats.
• Lymphoma occurs in various primary anatomic sites, such as the gastrointestinal tract, kidneys, mediastinum (chest cavity) and spleen.
• Unlike in dogs with lymphoma, cats generally do not present with generalized lymph node enlargement.
• The occurrence of feline lymphoma has been strongly associated with infection by the feline leukemia virus (FeLV) and certain strains of the feline immunodeficiency virus (FIV.)
• Combination of 5 chemotherapy drugs is reported to be the most effective method to treat lymphoma in cats.
• Radiation therapy and surgery, along with chemotherapy, are used to treat more localized forms of lymphoma (such as intra-nasal or ocular.)
• Treatment goals are to improve quality of life by achieving remission with minimal toxicity and side effects from the drugs.

What are the various anatomic sites affected in cats with lymphoma?

Areas that can be involved include the gastrointestinal tract, the mediastinum, the lymphatic organs (lymph nodes, liver, spleen and/or bone marrow), and miscellaneous locations. These less common areas include the kidneys, the eye (ocular form), the central nervous system, the nasal cavity, the skin and other areas.

How is lymphoma diagnosed in cats?

The most common methods used to diagnose lymphoma include fine needle aspiration, cutting needle biopsy or endoscopic biopsy. Occasionally a blood test may reveal circulating cancerous lymphocytes. Depending upon the site of the lymphoma, the appropriate diagnostic method may require general anesthesia.

Are there other tests recommended once lymphoma is diagnosed?

Often blood tests, radiographic studies, and sometimes bone marrow aspiration are needed to stage the lymphoma, to determine the extent of the cancer. The diagnostic work-up should include a complete blood count, platelet count, biochemistry profile and urinalysis. These tests also help to identify the existence of other unrelated illnesses (such as kidney disease) which may interfere with our ability to safely administer chemotherapy. Thoracic and abdominal radiographs, abdominal ultrasound and CT scan or MRI tests may be needed to determine the extent of the tumor. If the liver, spleen or kidneys are enlarged, ultrasound-guided fine needle aspiration is recommended to determine if these organs are infiltrated with lymphoma cells. A blood test for FeLV and feline immunodeficiency virus (FIV) is recommended to establish a prognosis for survival time and possible virus-associated complicating illnesses.

How is feline lymphoma treated?

Because lymphoma is a systemic disease, chemotherapy is the preferred treatment modality. In selected cases, prior to the administration of chemotherapy, radiation therapy or surgery may be used to treat lymphoma localized to a defined site.

It is important to understand that lymphoma is not curable.  Therapeutic success consists of achieving prolonged remission (control) of the lymphoma and associated clinical signs.  We strive to avoid toxicity or side effects from chemotherapy that interfere with the patient's quality of life.  The duration of remission is extremely variable, depending on tumor location, extent of tumor within one or several sites and presence of other mitigating circumstances (ie. anemia, kidney disease).  The chemotherapy drugs used to treat this cancer are a combination of oral and injectable medications administered at specific time intervals.  This is termed a chemotherapeutic protocol and is formulated specifically for each individual case.  The treatment approach associated with the longest remission and survival times involves weekly treatments for 2 months followed by biweekly treatments to complete a 6-month treatment period.  Alternative options do exist. The schedule of treatments will be reviewed as well as required tests during the treatment period.

What is the success rate with therapy?

The likelihood of achieving remission and the duration of remission depends upon the location and stage of the cancer as well as the treatment protocol administered.  For example, only 25-30% of patients with gastrointestinal lymphoma achieve complete remission. The duration of remission for patients with gastrointestinal lymphoma to whom chemotherapy is administered varies from 2 to 8 months, with the rare patient exceeding one year of remission time.  FeLV status in some cases can be a negative predictor of survival time.  Previous administration of prednisone may interfere with prolonged remission times.  In general, patients with more widespread effects of the cancer do not respond as quickly nor for prolonged periods of time.

How do cats respond to chemotherapy?

Most cats tolerate chemotherapy very well.  It is our experience that > 75% of pet owners are satisfied with their pet's quality of life while receiving treatment.  As lymphoma is not curable, our emphasis is placed upon this enhanced quality of life while undergoing therapy.  Acceptable side effects may include loss of appetite, vomiting, diarrhea and listlessness for 1-2 days following treatment.  These effects are fortunately self-limiting.  Occasionally, a chemotherapy dose reduction may be required to mitigate side effects.

Occasionally we encounter patients to which chemotherapy in pill form cannot be given.  In these cases, we can adjust the protocol to include only injectable medications.  A small percentage of patients experience unacceptable side effects from chemotherapy.  Persistent severe vomiting, diarrhea, low cell counts and poor quality of life necessitate discontinuation of therapy and allowing the lymphoma to follow its natural course.

Why do we treat cats with lymphoma?

Our feline pets are an integral part of our lives and our family.  The decision to pursue therapy for a malignancy in a beloved pet is a difficult one.  The emotional concerns,  financial obligations and time invested are important factors to consider.  Our objective is to extend the pet's life with good quality time.  Both the pet and all members of the family should enjoy this extra time.

What is the cost of treatment?

We will review the costs of all diagnostic tests indicated to determine the type and extent of the cancer.  All options for treatment will be discussed, as well as the costs associated with them.  Please do not hesitate to ask questions and review our discussions when you feel the need to do so.

Is this contagious to other cats?

Lymphoma is not contagious to other cats or humans.  However, if the patient is FeLV positive, other cats in the household should be tested for this viral infection.¨