LYMPHOMA IN CATS
One of the more common cancers of middle aged and older cats is Lymphosarcoma, commonly known by its older name, Lymphoma. It accounts for 33% of all cancers in cats, and 90% of those that spread to multiple organs in the body. Lymphocytes are a type of white blood cell. Lymphosarcoma is cancer of these white blood cells.
White blood cells are made in the bone marrow and in the lymph nodes, and there are several different kinds. White blood cells can be found everywhere in the body, since they are part of the immune system, and travel around the body fighting infections. This is why this form of cancer can be found in many different places and spread easily from one place to another.
As with many other cancers, there is a milder version and a more severely cancerous version. The less aggressive type tends to spread slowly in whatever organ it originated in and is slow to travel to other organs or invade other tissues. This type is very responsive to chemotherapy, with a high success rate for treatment. The treatment consists of a chemotherapy drug in tablet form that is given by the owner at home for three days in a row every 3-4 weeks. Prednisolone (a steroid) is also given orally. These drugs are given for the rest of the cat’s life, with periodic blood testing to monitor for side effects – every three weeks at first, then every 3-4 months if all is going well. We have had cats live three years or more with their disease, with good quality of life, and few or no side effects.
The more cancerous type of Lymphosarcoma requires much more intensive treatment and has a much lower survival rate. Even so, depending on the type of lymphoma, and the location and symptoms, some cats will respond to medication and maintain remission from their cancer for many months.
One of the most common syndromes we see with Lymphoma is the alimentary form of the disease, which means that it is located somewhere in the gastrointestinal tract – the stomach, the small intestine and/or the colon. Symptoms include weight loss, poor appetite, vomiting, diarrhea, blood in the stools or occasionally constipation. Many times we will see a cat who is losing weight with no other symptoms. This can make diagnosis difficult, as there are many diseases that cause weight loss, including kidney, liver, heart, thyroid and other digestive disorders.
Other syndromes for Lymphoma include the mediastinal form, in which the cancer starts in a large lymph node in the chest and leads to labored breathing, coughing or fluid in the chest; a renal form, where the cancer is located in the kidneys; a multicentric form that tends to spread quickly everywhere – liver, spleen, lymph nodes, eyes, brain or spinal cord, almost anywhere in the body.
Cancer is usually diagnosed with biopsies – taking small samples of the tissue that is affected to analyze under the microscope. Depending on where the cancer is located this may be easy or difficult. For the alimentary form, biopsies are done on the stomach & intestines. This can be done using a non-invasive method with a fiberoptic scope, or via abdominal surgery. If vomiting is severe we usually do the abdominal surgery, as we are looking for other causes of vomiting as well, such as obstruction by a foreign object. If the symptoms are chronic low-grade vomiting, weight loss, poor appetite or diarrhea the fiberoptic scope is usually the preferred method, as it is non-invasive.
We often recommend an ultrasound of the abdomen & internal organs before doing biopsies. The ultrasound scan can reveal whether the intestines are thickened, which would support a diagnosis of IBD or lymphoma. It also can reveal abnormalities of the liver, spleen, abdominal lymph nodes or kidneys. If any of these organs look abnormal, using a long needle guided by the ultrasound image, the internist can get tissue biopsy samples of these organs to use for diagnosis without the need for surgery. (This is not possible to do on the stomach or intestines, because poking a needle in and out of these organs lets digestive fluid and bacteria into the body cavity, causing peritonitis, which is a severe abdominal infection.) The ultrasound scan may also reveal pancreatitis, which is yet another cause of chronic vomiting, diarrhea and weight loss in cats.
Whether we diagnose lymphoma via ultrasound guided biopsies or surgery, once we know what is wrong, we can consult with an oncologist about the most effective course of treatment. If the diagnosis is the low-grade form of the disease, we strongly recommend that owners pursue treatment, as it is successful in 2/3rds of the cases we see. The high grade form has a poor prognosis and most owners choose uthanasia rather than more extensive chemotherapy, but for the right owner and the right cat treatment may still be a good option.
Pet owners always need to balance the need for treatment against the temperament of the cat. The more difficult a cat is to medicate, or the ore frightened or aggressive when handled, the less likely it is that treatment will allow a good quality of life for the cat – or the owner. We never want the last weeks or months of a pet’s life to be spent hiding, nor do we want the caregiver to feel overwhelmed or guilty over having to do procedures over and over again that are stressful. That said, most cats will take prednisolone crushed in canned cat food or tuna, and the pills for the low-grade form of Lymphosarcoma are only given for a few days each month. Many cats are very tolerant of the treatments, and have very few side effects, if any, from the medication.