Treatment Options for Veterinary Cancer Patients
Cancer (a.k.a. malignancy, malignant tumor, neoplasia) is a group of diseases involving uncontrolled, abnormal cell growth with the ability to invade or spread to other areas of the body. If untreated, it can often lead to serious illness and sometimes life-limiting complications. An exact cause of cancer is rarely identified in an individual veterinary patient; although, exposure to carcinogens (e.g. sun, cigarettes) and inherited abnormal DNA have been associated with some specific types of cancers in human patients. Metastasis is the process of cancer spreading from a primary tumor site to other areas throughout the body. During this process, tumor cells enter the blood or lymphatic vessels and travel to other areas of the body to form new tumors.
If cancer is suspected, diagnostic recommendations may include lab work, x-rays, ultrasound, fine needle aspirates, biopsies, and/or advanced imaging, such as a CT or MRI. In veterinary medicine, cancers are generally grouped into 3 categories: 1) carcinomas (tumors derived from epithelial tissues), 2) sarcomas (tumors derived from connective tissues), and 3) round cell tumors (tumors derived from blood or immune cells). In addition to a definitive diagnosis, diagnostic tests may also provide a tumor “stage” and a tumor “grade” in some cases. “Stage” describes tumor size and where it has spread in the body. “Grade” describes what the cancer cells look like under a microscope following a biopsy. Staging and grading systems are different for different types of cancer. In most cases, lower stage and grade indicate a more favorable prognosis.
After all of the pertinent results are obtained, the data points are integrated to provide comprehensive information regarding treatment options and prognosis. All cancers are not created equally; species, location, and diagnosis are very important to consider when determining a plan of action for an individual patient. Rates of growth and metastasis, response rates to various treatments, and prognoses can vary significantly based on these factors. Treatment options in veterinary oncology may include one or more of the following:
1) Surgery: Surgery is the first step in treatment for many localized tumors. It generally involves removal of the tumor itself plus a good margin of normal tissue around the tumor in order to prevent recurrence. Debulking is sometimes an option for large tumors or tumors in difficult locations in order to reduce the tumor to microscopic levels for improved success with follow-up treatment.
2) Radiation therapy: This is another form of localized therapy that uses high-energy radiation to kill cancer cells and improve quality of life. “Definitive” radiation therapy is generally used post-operatively for narrowly or incompletely removed tumors to help prevent recurrence, and a good long-term outcome is usually expected. “Palliative” radiation therapy is generally used for short-term pain control and relief from clinical signs when an incurable tumor is diagnosed.
3) Chemotherapy: Chemotherapy is a systemic form of treatment that is given either orally or as an injection with the intent to kill rapidly dividing cancer cells. It can be used alone for cancers/tumors that affect multiple areas of the body, such as lymphoma, leukemia, and metastatic tumors. Or it can be used in combination with surgery and/or radiation therapy to slow or stop localized tumors from spreading to other areas of the body when this is a concern. Different chemotherapy protocols are used for different types of cancer/tumors and all are usually very well-tolerated.
4) Targeted therapy: This is a new type of chemotherapy that acts selectively against molecular targets expressed by some tumors and can interfere with tumor growth and progression. The effect is different from the nonspecific destruction associated with traditional chemotherapy, which will kill any rapidly dividing cell population within the body (cancer cells and normal cells).
5) Immunotherapy: Immunotherapy is a medical treatment that induces, enhances, or suppresses an immune response. The goal of immunotherapy as a treatment for cancer is to stimulate the patient’s own immune system to reject and destroy tumor cells. Options for immunotherapy in veterinary oncology are currently very limited, but there is ongoing research in this area.
6) Clinical trials: Clinical trials evaluate the safety and effectiveness of new drugs and may offer a treatment option that potentially utilizes the newest medical research available. Some of these products are early in development, while others have been used in pets before. Details such as funding, the duration and intensity of the visit schedule, and potential side effects of the investigational product will vary from trial to trial.
8) Palliative/supportive care: This is a type of medical care that provides relief from the symptoms, pain, and stress associated with cancer. The focus of this type of treatment is on improving quality of life and not on curing the cancer. Fluids, physical therapy, urinary bladder expression, and medications for pain, inflammation, and nausea are just some of the palliative measures that can be considered.
All veterinary cancer treatment plans are customized to meet the needs and goals of the individual patient and family. A combination of different treatment types often provides the best chance for a good long-term outcome.
Dr. Mallett graduated from the University of Georgia College of Veterinary Medicine. She completed a one year internship in small animal medicine and surgery at Florida Veterinary Specialists followed by a three year residency in medical oncology at the University of Georgia. Dr. Mallett is board-certified in medical oncology by the American College of Veterinary Internal Medicine and is part of The Oncology Service at Friendship.
*Featured image courtesy of Dogs Naturally.