CANCER & CHEMOTHERAPY IN COMPANION ANIMALS

A cancer is a tissue mass characterized by persistent, excessive, and disorganized cell growth that is unresponsive to normal control mechanisms. Cancer is a leading cause of death in dogs and cats. Why this happens, in most cases, is not yet known. As a result of improved owner and veterinary care, pets are living much longer and thus are more susceptible to diseases of old age, such as tumors. Compared to people, dogs develop tumors twice as frequently, but cats only half as frequently. If your pet is thought or known to have cancer, a consultation with a veterinarian experienced in oncology can provide you with valuable information regarding treatment options and expectations.

Terms Used in Cancer Medicine:

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Tumor: simply means a "swelling," which may or may not represent cancer.
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Benign Tumors: have many normal growth characteristics. They do not "spread" or invade other organs. They, may however, compress body organs or tissues by virtue of their size. Surgical removal is usually curative.
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Malignant Tumors: often have rapid, irregular growth characteristics. These tumors can invade normal, local tissues, as well as spread to other tissues (especially the liver and lungs). New tumors can grow at these secondary sites, eventually causing the demise of the patient.
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Metastasis: the process whereby a tumor spreads to secondary sites. These new tumors are referred to as "metastatic"," or "metastases."
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Oncology: refers to the study of tumors, including their biological behavior and treatment.
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Remission: denotes a decrease in tumor size (often called "tumor burden") over time. Remission time is the length of time in which the tumor is under control.

Currently, treatment of cancer in animals can often result in fairly lengthy, good quality remission times. That still means that for many types of cancers, their return is inevitable. This fact must be contemplated and discussed before the client and the veterinarian decide to treat an animal for cancer. Having reasonable and accurate expectations will provide a more positive experience for all those involved.

Types of Cancer Treatments

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Surgery: surgical removal of tumors is a very common and valuable approach for solid tissue tumors. It can be used for soft tissue as well as for bone tumors. It can sometimes be curative on its own, if the disease process is localized and detected very early.
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Radiotherapy: or "radiation" therapy is available at large veterinary institutions such as Tufts University School of Veterinary Medicine (North Grafton, Massachusetts) and Angell Memorial Animal Hospital (Boston, Massachusetts). It consists of the use of a radioactive beam to damage and/or kill malignant cells in a localized area. It can offer good quality remission times for many types of tumors, but usually not cure. Animals are surprisingly tolerant of radiation therapy
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Chemotherapy: is the use of certain drugs alone, or in combination to control tumor growth. All of the drugs currently given to animals are human anti-cancer drugs. Fortunately, many of the negative consequences of their use in human medicine are not experienced in veterinary medicine. Chemotherapy and/or surgery are the two most important treatment modalities in veterinary cancer medicine. A combination of therapies may also be indicated in certain cancers. Some cancers require a specific, brief number of treatments, while others requiring ongoing treatment to maintain remission.

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