Chemotherapy is a word which carries a heavy burden of negative associations for most people. People are often very sick while undergoing cancer chemotherapy. However, the treatment process is different in many ways for our beloved companions.
Veterinarians use chemotherapy to give pets with cancer a longer life than they would otherwise have, but more importantly, to make life more comfortable. Our goal in cancer treatment is to minimize the negative aspects of treatment so that the pet can have the best life possible.
Cancers are diseases caused by cells which are replicating out of control, forming a population of clones. The “parent” cell is a normal cell in the body. The different kinds of cancer are designated by what kind of cell that parent cell was, such as a bone cell, a skin cell, or a blood cell. This tells us the “family” the cancer belongs to.
Often, the cancer is then further categorized by how abnormal the cells appear, or whether they have spread to other parts of the body. This process is called staging. Staging is used to determine the prognosis for that patient, and the relative likelihood of response of the patient to treatment.
Two broad categories of cancers are those that form a mass (or growth), and those that are diffuse. For example, many cancers in the skin form a lump that you can feel, and which can be surgically removed. Cancer of the blood cells can spread throughout the body, traveling around in the bloodstream, and cannot be surgically removed (like lymphoma). For most cancers in which a mass forms, the first line of treatment is removal of the mass, and chemotherapy comes afterwards. For those in which there is no mass to remove, chemotherapy is usually the first line of treatment.
Metastasis is when cancer cells spread from a primary site (a mass) to other parts of the body. Many of the tests that are performed prior to initiating chemotherapy are focused on determining whether the cancer has metastasized. If no metastasis is identified, then the cancer either has not spread, or the spread is yet not detectable.
If metastasis is identified, the likelihood of any meaningful response to chemotherapy is poor, and hospice care is the next recommendation. Chemotherapy is used primarily for those patients with cancers that are likely to metastasize, but that have not yet done so. Chemotherapy drugs suppress the growth of any escaped calls, prolonging survival time of the patient. Rarely, they kill all the cancer cells, resulting in a permanent cure.
At Veazie Veterinary Clinic, chemotherapy treatment is performed by trained, licensed technicians in a dedicated space. There is a room used only for chemotherapy patients in the Wellness Center. This room is equipped with cages, all the materials needed, and special tools used to safely handle and administer the medications.
Chemotherapy administration varies with the drug. In general, the patient comes for an appointment in the morning, and has a physical exam and a CBC. If everything is going well, then the patient is admitted to the hospital for treatment. The anti-nausea medication is given. Some patients are given a mild sedative to make the process easier for them. Most chemotherapy drugs are given into a vein, so the area is cleaned and prepared with a local numbing agent to make them comfortable. An intravenous catheter is placed. Different drugs are given over different periods of time. Some drugs require the patient to be in the hospital for most of the day, but the majority can go home after a few hours.
Other than monitoring closely for changes, little aftercare is needed. Most patients are quiet for a day or two, and some have mild side effects as described above. Families are advised not to have major contact with any bodily fluids from the patient for several days, and to use gloves or other disposable materials to clean up any accidents. Pregnant owners should not clean up any wastes at all, and should avoid significant saliva contact for about 3 days. Most patients quickly return to their regular daily activities.
When Chemotherapy is Finished
Chemotherapy protocols have an end. Many drugs are only given for a set number of treatments. Once this is complete, recheck examinations are scheduled to monitor for any detectable recurrence of the cancer. If this happens, additional chemotherapy is an option for some, but not all cancers.
Some patients are given medications at home for the rest of their lives. This is called metronomic therapy, and can help to slow the return of the cancer. For most canine and feline patients, chemotherapy does not eradicate the cancer, but provides more time and relief from discomfort.