By Dr. Alice Villalobos
Director, Pawspice and Animal Oncology Consultation Service
Many cats with lymphoma will do well with treatment; however, we don’t have a test to predict which cats will do poorly. Feline Leukemia Virus (FeLV) and Feline Immunodeficiency Virus (FIV) play an underlying role as the causative agent for genetic mutations found in feline lymphoma cancer stem cells (lymphoblasts). The effects of these two retroviruses that are present in the cat’s system may cause related or paraneoplastic syndromes and a low red blood cell count (anemia). Education about this “viral factor” must be provided to each cat’s family members so they can evaluate the challenges that their beloved cat must deal with. Cats present to us in basically one of three different clinical stages of disease: the truly ill, the mildly symptomatic and the unaffected or asymptomatic. We have less optimism because we see less response in the very sick, frail cats and in the cats with anemia. We see more success in sick but stable cats that have good appetites. We see good to great responses with the asymptomatic cats.
Historically, young cats with lymphoma and fluid in their chest (anterior mediastinal mass, AMM) would generally die quickly without the help of a rapid diagnosis and immediate treatment. I once wrote a letter to all L.A. emergency room hospitals and asked the attending veterinarians to please examine the drained chest fluid and check for lymphoblasts immediately. If they waited for the laboratory to confirm the presence or absence of these tell-tale cells, the cat would get worse. I also asked the doctors to perform a percutaneous fine needle aspiration (FNA) of the mass anterior to the heart with a 25 or 27 gauge needle if there was no free fluid. If even one lymphoblast is found in the drained fluid or in the FNA sample of the chest mass, the cat should be treated for lymphoma with IV Dexamethazone and vincristine immediately. This would shrink the mass within hours and give the poor cat a chance to breathe better within a few hours and survive the threat and pain of suffocation. Anything short of this quick action creates delay and clinical deterioration and sadly early euthanasia. It is a shock to the cat’s family because their young cat was healthy just days before! Since this form of lymphoma had over an 80% response rate, I failed to see why emergency doctors that were quick to remove the spleen of dogs with blood in their abdomen (hemoabdomen), would hesitate to give chemotherapy to these lymphoma cats.
Today, most our feline lymphoma cats come are diagnosed with gastro intestinal (GI lymphoma) or with enlarged abdominal lymph nodes (mesenteric lymphoma).
The typical signs and history are weight loss, soft stool, diarrhea or vomiting. These signs should alert cat lovers and their veterinarians to suggest a work up to see if the cause is inflammatory bowel disease or lymphoma. Cats with ropey intestines, palpable mesenteric lymph nodes, or intestinal obstructions are highly suspect for GI lymphoma.
Cats that have the diagnosis of inflammatory bowel disease (IBD) are at greater risk of developing intestinal lymphoma. It is well understood that IBD is considered a precancerous condition and the lesions may transition into lymphoma in a significant percentage of IBD cats. The tricky part is knowing when to abandon the treatment for IBD and go to the more specific chemotherapy medications that are needed to put the lymphoma into remission.
My favorite way to diagnose palpable abdominal or GI lymphoma in cats is via fine needle aspiration (FNA) cytology. I use a 1-½ inch 27 gauge needle to safely aspirate any structure in the abdomen. Ultrasound guided FNA of mesenteric nodes and thickened bowel loops is another excellent way to get a non-surgical diagnosis. The next method that bypasses the stress of exploratory surgery is with endoscopy, which uses a fiber optic instrument to identify and sample abnormal tissue in the GI tract. Despite the fact that the lymphoma lesions may be below the mucosa for the endoscopic biopsy technique, enough cats are definitively diagnosed without the stress of abdominal surgery. Laparoscopy is becoming more available to target lesions for biopsy in private practice. Cats that are weak and thin would be best served if the diagnosis could be made via FNA, endoscopy or laparoscopy without open abdominal surgery. Finally exploratory surgery may be elected as the only sure method to harvest multiple organ tissue and full thickness intestinal samples.
Some cats will present with enlarged kidneys or enlarged livers (hepatomegaly). Ultrasound and FNA can quickly establish the diagnosis for immediate treatment. We celebrate the responses and report that we have some very long-term survivors that presented with advanced kidney disease or with hepatic compromise. Many cats can respond to aggressive immediate treatment if they are supported with fluid therapy and nutritional support with hand feeding or esophageal feeding tubes. It is possible to rescue cats from near fatal conditions induced by lymphoma and to restore their well-being. Their families are very grateful! If there is little to poor response in the first month of treatment, the prognosis for the non-responders changes to poor to grave.
Cats that are FeLV and FIV negative have a better prognosis. It is important to know that one of these viruses may be hidden in your cat in a dormant form and is most likely the cause of the lymphoma. In viral negative cats, the survival can be expected to last for one to several years. Many of our feline lymphoma cases are enjoying 2-5 year plus remissions. Some patients have even been discontinued from their chemotherapy.
Chemotherapy for Feline Lymphoma
My favorite protocol for cats is the Modified Wisconsin Protocol. We administer vincristine at 0.5mg/m2 or at O.O25mg / kg I.V. along with 400 iu/kg of L-asparaginase S.Q. on the first day. As a pretreatment for the L-asparaginase, we give dexamethasone SP at 0.1ml to 1 ml I.V. prior to the vincristine injection using the higher dose depending on the magnitude of the cat’s tumor burden and the symptoms. Prednisone at 5mg B.I.D. forever is dispensed along with two tablets of 25 mg Cytoxan to be used orally on day #8 and #9. We instruct the carers to return on day #15 for Adriamycin at 1mg / kg IV. We also administer dexamethasone as above as a pretreatment. We instruct the client to return in one more week for vincristine as above on day #21 and then repeat the Cytoxan day #28 and #29 and then the second Adriamycin as above on day # 32. Thereafter we use a 10-day interval between treatments. The cat returns for vincristine every 21 days for 6 months. Ten days after the vincristine, the owner is to rotate the Cytoxan with oral Chlorambucil giving one 2mg tablet B.I.D. or one tablet two days in a row only.
We place the entire chemotherapy regimen onto a calendar for the client to use as a guide. This calendar is important. We ask our carers to keep notes on how their cat is doing on the calendar. After one year the interval between treatments may be extended to two weeks. For those clients who cannot return every 3 weeks, the schedule may be adjusted to using the Chlorambucil 10 days after the vincristine and the Cytoxan 20 days after with a return at 30-day intervals for IV. vincristine. Further adjustments may be made to accommodate our caregivers’ budgets, etc.
In response to caregiver’s requests, I have developed a few stay at home oral chemotherapy protocols. One is called the “LU-C-LO-V” protocol. It incorporates LO for Lomustine at 50mg / m2 divided over 3-4 days after the LU, which is for Leukeran (Chlorambucil) the C is for Cytoxan. This protocol can be introduced to long-term cases and although it seems to help keep lymphoma cats in remission and at home, results are not compiled for reference.
All cats must be monitored for low white blood cells (leukopenia) low platelets (thrombocytopenia) and low red blood cells (anemia). This is accomplished by a blood complete blood test known as the CBC just prior to chemotherapy. Decisions for changes in dose and sequence of the chemotherapy medications are made based upon the CBC and a panel that monitors the function of your cat’s internal organs. Your cat may also need detailed medical support for ongoing clinical symptoms and other pre-existing disease conditions such as obesity, diabetes, chronic kidney or heart disease, etc. Our Pawspice Team truly works hard to achieve remissions and we feel rewarded with each one of our miraculous responses and long term survivors that we have successfully achieved over the 40 plus years of treating lymphoma cats.