What is Feline Lymphoma?
Lymphoma is one of the most common types of cancers found in cats. It is a cancer of the lymphocytes, which are white blood cells that are part of the immune system. They are found throughout the body and are responsible for helping the body fight off infections. Lymphoma can occur in many areas of the body including the gastrointestinal tract, kidneys, liver, lymph nodes, skin, chest cavity, and nasal cavity. The gastrointestinal tract is the most common region affected. Generally, lymphoma is found in older cats, with males being slightly more predisposed than females. Cats that are FIV or FeLV positive are more likely to develop this disease.
What are the Clinical Signs?
Clinical signs typically depend upon the location or organ system involved. Common signs include vomiting, diarrhea, weight loss, decreased appetite, and lethargy. Other symptoms can include respiratory distress (if the chest or nasal cavity is involved), increased water consumption and urination, nasal discharge, and/or facial swelling. If the cancer presents as a large mass, it is important to find out whether organ function is affected (i.e. GI tract, kidney, liver).
How is it Diagnosed?
The main method of diagnosing feline lymphoma is with a fine needle aspirate or biopsy of the affected organ or tissue. Once a diagnosis has been made, staging is recommended. Staging consists of several diagnostic tests to help determine the extent of disease. Bloodwork consists of a CBC to assess the red blood cells, white blood cells and platelets, a chemistry panel to look at organ function, and a urinalysis. Radiographs of the thorax are taken to look for intrathoracic lymph node enlargement and/or lung involvement. An abdominal ultrasound is performed to look for liver, spleen, kidney, stomach, intestinal or lymph node involvement. Lymphoma is categorized as high (large cell) or low grade (small cell), which determines the biological nature of the tumor. Once the cancer is graded and staged, we can determine the prognosis for your pet’s presentation, and customize his or her treatment.
What are the Treatment Options?
Though feline lymphoma is generally an aggressive cancer, there are several treatment options. Chemotherapy is very effective at treating lymphoma. The goal of chemotherapy is to get your pet into remission for as long as possible with minimal side effects. The “gold standard” for treating high-grade gastrointestinal lymphoma in cats is a multi-agent chemotherapy approach. This involves the use of prednisone (a steroid that has anti-tumor activity), along with four other chemotherapy drugs. This therapy generally offers the longest disease free interval, but is expensive and requires frequent reassessments over a 4-6 month period. There are other less intensive chemotherapy protocols, but the remission times are not as long. For low-grade lymphoma, chemotherapy is recommended, but it is not as intense as previously described, and can consist of oral medication that is given at home.
There are some cases where surgery (solitary intestinal mass, especially one that is causing an obstruction) or radiation therapy (nasal lymphoma) can be used. If these treatments are used, it is recommended that they be used in conjunction with chemotherapy.
For owners that decide not to pursue chemotherapy for a variety of reasons, we recommend prednisone therapy. Prednisone, as discussed above, has some anti-tumor activity, but is mostly used to make your pet feel better. A median survival time of 1-2 months is associated with prednisone use alone for high grade lymphoma.
What is the Prognosis?
Prognosis for feline lymphoma is most commonly predicted by the grade (high vs low), the severity of clinical signs upon presentation, location of the disease, his or her viral status, and initial response to therapy. Small cell lymphoma (low grade) is associated with an excellent prognosis with most cats living two or more years on oral chemotherapy at home. However, high grade lymphoma (large cell) is associated with a poorer prognosis with the majority of cats succumbing to the illness within the first year after diagnosis. Cats that have severe clinical signs upon diagnosis and/or are FeLV positive typically carry a worse prognosis. Extranodal presentations such as central nervous system, renal, or bone marrow involvement often carry a less favorable prognosis even with aggressive therapy. Conversely, nasal lymphoma carries a more favorable prognosis. Initial response to chemotherapy, usually noted within the first 3-4 weeks of treatment, is highly prognostic with cats that have a complete response early on having a significantly improved prognosis over those cats that do not respond.
Chemotherapy for Feline Lymphoma
Lymphoma is considered to be the most chemo-responsive cancer in cats and treatment with multi-agent chemotherapy is associated with the longest survival times. Common protocols include ACOPA and Madison Wisconsin, but both utilize the same chemotherapy agents. The induction part of the treatment protocol ranges from 21-25 weeks. The goal of induction chemotherapy is to induce a remission while preserving a good quality of life for cats undergoing treatment. When a cancer such as lymphoma is no longer detectable based on physical exam, radiographs (x-rays), and/or ultrasound, the patient is considered to be in complete remission. A complete remission is expected in up to 70% of cats receiving multi-agent chemotherapy.
A maintenance chemotherapy protocol is sometimes recommended following induction based on individual cases. Maintenance chemotherapy is less intensive than induction chemotherapy and consists of intravenous treatment, Vincristine, in the veterinary hospital every 21 days along with oral medications, including prednisone, given at home.
The information below outlines the most commonly used chemotherapeutic drugs for cats with lymphoma.
- L-Asparginase: The first chemotherapy drug given to patients is typically L-Asparginase more commonly referred to as Elspar. Elspar is an intramuscular injection that works quickly in destroying lymphoma cells by depriving these cells of a food source that they need to survive. Side effects of L-asparginase are uncommon but include allergic reactions, isolated vomiting, pancreatitis, and a phenomenon called acute tumor-lysis syndrome which is the result of large numbers of cancer cells being destroyed at one time causing overwhelming inflammation in the body. Hematologic toxicity is rare with Elspar. Overall, side-effects with Elspar are seen in less than 1/500 cases treated.
- Vincristine: During the protocol, patients routinely receive Oncovin, more commonly known as Vincristine. Vincristine is a chemotherapy drug that must be given intravenously. It can cause tissue irritation if the drug leaks out of the vein. Side effects of vincristine can include a reduction in appetite, vomiting, constipation, and occasional diarrhea. Side effects of this drug will typically occur in the first 24-72 hours after treatment. If vomiting, diarrhea or poor appetite continues for more than 24-36 hours, call your oncologist for treatment and care recommendations.
- Cytoxan: Cytoxan, also known as cyclophosphamide, is given alone or sometimes in conjunction with vincristine. Cytoxan is administered orally in a tablet form or as an intravenous injection. The main side effects of Cytoxan include vomiting, diarrhea, and suppression of the body’s white blood cells. If vomiting and diarrhea occur, it is typically minor and only 1-2 days after treatment. Because Cytoxan causes reduction in white blood cell counts, a complete blood count (CBC) is recommended 7 days after treatment. Extremely low white blood cell counts are addressed with antibiotics to help prevent life-threatening infections.
- Doxorubicin: Adriamycin, more commonly referred to as doxorubicin, is also received routinely during the protocol. It is given intravenously through a well-placed IV catheter due to the fact that significant tissue damage can occur if doxorubicin is given out of the vein. The treatment with doxorubicin, an infusion, typically takes ~30 minutes. Some cats need mild sedation given the need for a secure catheter with this treatment.
- The side effects of doxorubicin include vomiting, diarrhea, reduction in white blood cell counts and occasional kidney-associated toxicity in cats. The patient should only experience one to two episodes of vomiting or diarrhea within the first 1-2 days of treatment. If either of these symptoms persist or are more severe, a veterinarian should be consulted. Due to the potential for reduction in white blood cell counts, a CBC is recommended 7 days after treatment. Before every treatment of doxorubicin, complete bloodwork and a urinalysis are recommended. The bloodwork and urinalysis are used to assess kidney function and white blood cell counts.
- If a cat has a prior history of kidney toxicity or develops changes that indicate reduced kidney function, a different drug, CCNU (lomustine), may be substituted for doxorubicin as a means to help preserve kidney function. This medication is given orally every three to four weeks. Side effects of this medication are similar to that of doxorubicin including vomiting, diarrhea, and white blood cell suppression. Over cumulative dosing, there is also a risk of liver toxicity. Serial bloodwork will be used to monitor for this complication.
- Prednisone: Prednisone is a corticosteroid that can be administered in a tablet, liquid, or injectable formulation. This medication is helpful in treating lymphoma and is often given throughout the protocol. Prednisone is typically well-tolerated in cats, but increased appetite and increased urination may be noted. Rarely, vomiting and diarrhea can be seen associated with prednisone treatment. A rare but significant side effect includes the development of diabetes mellitus. Blood glucose is monitored routinely while this medication is being administered.
The goal of chemotherapy treatment is to control the cancer while helping pets maintain a good quality of life. Compared to humans, chemotherapy treatment for pets is less intense with fewer side effects and with the use of oral anti-diarrheal and anti-nausea medications at home, typically most cats recover within 24 hours. If vomiting, diarrhea or poor appetite continues for more than 24-36 hours, call your oncologist or primary veterinarian for treatment and care recommendations.