Because of improved nutrition, preventative health care and advances in veterinary medicine, our pets now live longer lives than they did in the middle of the last century. Ailments like parvovirus, heartworm disease, and taurine-related cardiomyopathy in cats are uncommon now, but because of the longer lifespans along with better diagnostics, we see more cases of cancer than ever. As frightening as that may be, we are also able to treat many of these pets and give them a good quality of life.
One of the most common cancers we see in dogs and cats is lymphosarcoma, commonly referred to as lymphoma. Lymphoma is a cancer of the lymphatic system, a series of vessels that carry white blood cells, fluid, nutrients and tissue waste products. Because these vessels travel all over the body, this particular cancer can occur almost anywhere. The lymph nodes, intestines, stomach, kidneys, liver and brain are just some organs that can be affected. Pets which have lymphoma often stop eating well and lose weight. They also may start drinking excessive amounts of water. Owners will sometimes notice lumps in the neck which are enlarged submandibular lymph nodes. On physical exam, we will often find that all the lymph nodes are enlarged. They are located in the neck behind the jaw, in front of the shoulders (prescapular), in the groin (inguinal) and behind the knees (popliteal). We can then take a sample of the lymph nodes with either a biopsy or a fine needle aspirate and send it to a pathologist for a diagnosis. Bloodwork is also indicated to see if any internal organs are being affected and to see if the cancer is in the bloodstream. Radiographs can show if there are changes in the size or shape of the organs and if there is any spread into the lungs. In the vast majority of cases, there is not a discreet tumor that can be removed, so the best option for treatment is chemotherapy.
The idea of performing chemo is distressing to many owners and their initial reaction is that they do not want to put their beloved pet through it. However, dogs and cats do not seem to have the same severe side effects that people do in most cases. They do not lose their hair (although I did have a patient in which the hair changed color). Sometimes vomiting or diarrhea can occur, but this can usually be controlled with medication. There is always a risk of infection because chemotherapy can decrease the white blood cell count.
There are several different protocols for treating lymphoma, but generally they all involve using a number of drugs which are rotated weekly or biweekly for several months. It is important to also monitor the pet’s blood counts in between treatments, so you can see that you, your pet and our staff end up seeing a lot of each other. The goal of the chemotherapy is to bring about remission, which means that the disease goes into an inactive state and the pet feels normal. Unfortunately, lymphoma in pets is generally not curable, but we can usually give them a good quality of life for one to two years.
In future columns, we will address numerous other cancers in pets. If you would like to know more or have any concerns that your pet is not acting right, please give us a call.