Cancer in Cats
As cats continue getting older because of better nutrition and veterinary care, the cases of cancer have also been on the rise. The bottom line is that cancer becomes more common in older cats and a lot more cats have been getting older. The good news is that treatment options are much better today than even a few years ago. Back in the 80’s when I thought my cat “Lynx” had a tumor, I can remember my mom telling us that she didn’t want the cat to be in pain, to get dehydrated, or to starve. Those were the rules that had to be adhered to whenever a decision was to be made regarding cancer treatment in a cat.
About a third of all cancers in cats are lymphomas. This lymphoid tissue is normally present in many places in the body including lymph nodes, spleen, liver, gastrointestinal tract, and bone marrow. The feline leukemia virus (FeLV) and the feline immunodeficiency virus (FIV) make cats more susceptible to developing this type of cancer. This cancer can occur at any age, sex, or breed. The veterinarian will usually check the lymph nodes or gastrointestinal tract, do an X-ray or ultrasound, get a blood chemistry workup, or do a biopsy. When lymphoma is diagnosed, treatment usually includes various drugs such as doxorubicin, cyclophosphamide, vincristine, and prednisone. In some cases radiation and or surgery have proven effective in treating a localized lymphoma that is not too spread out into various organs. A cat with lymphoma will usually survive only a month or two after diagnosis; however, if that same cat is treated it can live up to 6 months, and in about a quarter of the cases the cancer goes into remission that can last for years.
Another kind of tumor is called Mast Cell tumors, and they originate in the bone marrow. Mast cell is an important part of the cat’s defense mechanisms. Mast cell tumors most commonly occur in the skin and usually are a danger to middle-aged or older cats. Once the tumor is found and graded from I to III (I being the least dangerous and III being the most dangerous), treatment is started with chemotherapy, radiation, or surgery. The drugs used are prednisone, lomustine, and vinblastine. Prednisone is a glucocorticoid hormone which has powerful anti-inflammatory actions. The most common side-effect observed is excessive thirst and urination as well as an upset stomach. Lomustine binds DNA therefore preventing it from replicating. Side-effects include suppression of the bone marrow, liver toxicity, and upset stomach. Vinblastine is in a class called vinca alkaloid that works by interfering with proteins and preventing cells from dividing.
Fibrosarcoma originates in the connective tissue and may spread to other parts of the body. This is the most common soft tissue tumor in cats. There are three types seen in cats: a multicentric form which is usually seen in very young cats and is caused by the feline sarcoma virus, a solitary form is seen in cats of all ages and it’s a cancer that has not been caused by the feline sarcoma virus, and the vaccine sarcoma is associated with the feline leukemia vaccine for the most part. The best way to prevent this kind of cancer is by avoiding unnecessary vaccinations. Surgery is usually the recommended treatment although chemotherapy and radiation may be used along with surgery to help prevent recurrence.
Mammary tumors are the third most frequently seen tumors in cats. These usually occur in older cats and at greater risk are Siamese cats, and unspayed females. This is an aggressive tumor that often finds its way to the surrounding lymph nodes and lungs. Treatment may include a complete removal of the glands affected. Radiation may be used to help prevent recurrence of the tumor. Chemotherapy has also shown complete responses in 50% of cats with these tumors. Usually a combination of doxorubicin and cyclophosphamide is used with some success.
One of the best things you can do for your cat is to visit the veterinarian if you notice something wrong like swelling of the lymph nodes or a tumor somewhere. The earlier the treatment is commenced the better for your cat, and the less suffering will most likely occur. The advice that I heard when I was younger from my mom still holds true today: to maintain any quality of life it is important to not let the cat hurt, try to keep the cat from vomiting constantly, and don’t let the cat go without food for too long. Quality of life is the most important thing and ultimately everything within reason should be done to ensure this is kept up. Your cat’s pain can be minimized with proper pain management which may include a pain patch containing fentanyl; the vomiting could be minimized by giving metoclopramide or dolasetron mesylate. To maintain or increase the appetite, cyproheptadine or megestrol acetate given by mouth have both proven successful.
As always if you have any medication related questions, please call your 1800PetMeds pharmacist who will be more than happy to answer them for you or at the very least can guide you in the best direction.