I see a lot of cancer in my cat practice. A major reason is that cats are living longer than ever before. Now that they’re living to 17, 18, (and even longer), they’re living long enough to develop cancers that we never saw when they died at 12 or 13. Another reason is that major medical advances have given us the technology to detect cancers that previously went undiagnosed. An increased awareness of cancer, coupled with more sophisticated technology, has allowed veterinarians to become pretty adept at making the dreaded diagnosis.
The diagnosis of cancer in a beloved cat can be devastating. However, it is important to realize that, as in human cancers, many types of cancer in cats can be treated, managed, and sometimes even cured. Chemotherapy is one of the most effective ways to treat cancer. Fortunately, the most common type of cancer that we diagnose in cats – lymphosarcoma – is very sensitive to chemotherapy. (Note: lymphosarcoma is sometimes called lymphoma. The terms are synonymous.)
I think the incidence of cancer is increasing. Last year, we diagnosed maybe four cases of high-grade lymphosarcoma. This year, we’ve diagnosed four cases, and we’re only half-way through March.
Chemotherapy is the treatment of cancer with anticancer drugs. The drugs are toxic to malignant cells. Some of these drugs are given intravenously. Others are given by mouth. In some cases, chemotherapy is the only line of treatment. In other cases, chemotherapy is given in combination with other modalities, such as surgery or radiation. For example, chemotherapy may be given after surgery or radiation to help slow the growth of cancer that may have already spread. In other cases, chemotherapy may be employed before surgery, to shrink the size of a tumor prior to surgery, or to make your cat more comfortable while living with the disease.
For many people, the word “chemotherapy” has terrible connotations, with visions of hair loss, vomiting, and other distressing side effects. Nearly everyone has some personal experience with chemotherapy, and many cat owners are concerned about “putting their cat through chemo”. The reality is that most cats handle chemotherapy very well. Cancer treatment for both people and pets has become more sophisticated over the years, and the side effects of the drugs we use have become less severe. In addition, the chemotherapy protocols used in veterinary medicine are less aggressive than those used for humans, so side effects, if they occur, are often very mild. In human medicine, the goal of treatment is to achieve a cure. In veterinary medicine, the goal of chemotherapy is to extend your cat’s life while maintaining its quality.
There are many different chemotherapy protocols. Some of the drugs used in these protocols are given by a simple injection. Others are infused intravenously over a few hours in the veterinarian’s office. Yet others may be given orally, at home by you. Some drugs are given daily. Others are given weekly, or once every three weeks.
Owners of cats who are undergoing chemotherapy are always concerned about possible side effects of chemotherapy. Fortunately, pets suffer fewer and less severe side effects compared to people. Chemotherapy works by attacking the rapidly dividing cells in the body. Cancer cells fall into this category, however, cells found in the intestinal tract, bone marrow, and hair follicles also fall into this category. Chemotherapy, therefore, may result in gastrointestinal upset, bone marrow suppression, and hair loss in some cats. Gastrointestinal upset may manifest as decreased appetite, vomiting, and diarrhea. Bone marrow suppression may lead to decreased production of white blood cells, which in turn can lead to an increased susceptibility to infection. As for hair loss, this is uncommon in cats. When it occurs, the whiskers are most commonly affected. For most chemotherapy, side effects begin three to five days after administration. Most cats experiencing gastrointestinal side effects can be managed at home; rarely is hospitalization required.
Most cat owners are pleasantly surprised at how well their cat does with chemotherapy. Most cats maintain a good quality of life, and it is very gratifying to have the extra time with a treasured companion.
Treating a cat with chemotherapy is a commitment – a time commitment, financial commitment, and emotional commitment – and it can be a bit of an emotional rollercoaster for cat owners.
Chemotherapy for low grade lymphosarcoma is pretty benign. Treatment typically consists of two drugs, prednisolone and chlorambucil, and most cats tolerate the drugs very well and go into remission which can last for months and months. In fact, one cat in our practice, “J” , is at month number 43 on chemo. She holds the record for our practice. Next is “O”, who is at month 31. Not bad!
High-grade lymphomsarcoma is a more aggressive cancer. Most of the cats I treat go into remission. Currently, we’re treating four cats. “B” was diagnosed with lymphosarcoma of the colon. It had spread to the lymph nodes at the time of diagnosis. We began our treatment protocol approximately 11 weeks ago. The cat instantly went into remission. The huge colon tumor had practically melted away after only two doses of chemo. It was fantastic. We’re at week 11 of chemo, and the cat is thriving.
“M” is a big sweet cat who had lots of sneezing and a chronic nasal discharge from one nostril only. Rhinoscopy and biopsy revealed high-grade lymphosarcoma. I forgot how far along he is in our chemo protocol (I think week 8), and he is in remission and doing great.
“O” is the third cat we diagnosed this year. She’s an interesting case. She was losing weight, and endoscopy revealed what was called “low-grade” lymphosarcoma of the stomach. After the diagnosis, we performed abdominal ultrasound to look for any other signs of cancer, and there were changes that suggested high-grade lymphosarcoma in the kidneys and perhaps a part of the intestine. We aspirated the kidneys, and indeed, the pathologist diagnosed high-grade lymphosarcoma. So, we switched from the low-grade protocol to the high-grade protocol. Now, after about six weeks of chemo, a recheck ultrasound revealed “O” to be in remission. The kidneys are normal and that small mass involving a portion of the intestine is no longer visible.
“L” is the fourth cat, and is perhaps not doing as well as the other three. She was diagnosed, many months ago, with inflammatory bowel disease. She was put on prednisolone and was doing fine. Then, she developed what I thought was an enlarged lymph node in her neck. I removed the node and sent it in for biopsy. It turned out that the lump was actually a salivary gland, and that there was low-grade lymphosarcoma in the gland. Nowhere else was there evidence of lymphosarcoma. So we added chlorambucil to our medical regimen, and she did great. Many months later, however, she began to lose weight. I suspected that her inflammatory bowel disease had flared up. We performed abdominal ultrasound and discovered, however, what looked to be cancer. There were nodules in the spleen, and the intestines looked suspicious for cancer. We aspirated the spleen, and the diagnosis was high-grade lymphosarcoma. “L” took her first treatment very well, but the drug that we give during week 2, called Cytoxan, seemed to make her feel poorly. Her appetite dropped and she lost weight. I was worried about her and was going to postpone the week 3 treatment, but she bounced back very well. We saw her today, and she was doing well, eating and being feisty as usual. We went ahead with her third treatment today. I’m hoping she gains the weight that she recently lost, and that the drug we gave today (adriamycin, a very potent drug) doesn’t cause any adverse effects. Every cat we’ve given it to has had no side effects, but “L” is the smallest and most frail of the bunch. I feel that she’ll do okay.
I find treating these cats rewarding. The vast majority do well, with no adverse effects, and my clients get to spend more quality time with their kitties. I’ll keep you all posted on how these cats are doing over the next few months.
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