Treating Tumors and Cancers in Dogs

The best possible treatment option is surgical removal of a cancer that has not spread. To prevent recurrence, a surrounding margin of normal tissue should also be removed. An initial approach that removes the tumor with an adequate margin of normal tissue may be the most important factor in controlling cancer. When a cancer recurs locally because of incomplete excision, the opportunity for cure is often lost. That's why surgeons speak of “clean margins,” meaning no cancer cells are found on the outer edge of the tissue removed.

A cancer that spreads only to local lymph nodes may still be cured if all the involved nodes can be removed along with the primary tumor. Even when a cancer is widespread, removing a bleeding or infected mass, or simply a large one that is interfering with a normal physical function, can provide relief and temporarily improve the quality of life.

Electrocautery and cryosurgery are two techniques by which tumors on the surface of the body can be removed. Electrocautery means burning off the tumor using electricity; cryosurgery involves freezing the tumor to remove it. These methods provide an alternative to surgical removal and are suitable for benign tumors such as papillomas. New surgery techniques may use lasers or hyperthermy-heat treatment Radiation therapy is used primarily for local tumors that have not metastasized. Many canine tumors are sensitive to radiation. They include mast cell tumors, transmissible venereal tumors, squamous cell carcinomas, cancers of the oral and nasal cavities, and soft tissue sarcomas. A potential disadvantage of radiation therapy is that it requires special equipment and must be done at a medical center. Radiation therapy can also be done to relieve pain, especially with very painful cancers such as osteosarcoma (bone cancer).

Chemotherapy is used to prevent and control the metastatic spread of cancer cells. However, most canine cancers are only moderately sensitive to chemotherapy. It can cure only one type of cancer in dogs: transmissible venereal tumors. When used as the only form of treatment, chemotherapy usually does not extend survival. Lymphosarcoma and leukemia are exceptions. Chemotherapy drugs, even when their use is tightly controlled, can have major side effects. In humans, chemotherapy is aimed at achieving a cure. Due to their lesser efficacy in dogs, chemotherapy is aimed at controlling the disease and giving the dog a period of remission. Lower dosages are generally used and many dogs do not have the severe reactions to chemotherapy that people do.

Cancer Treatments

  • Surgery- Surgery can totally remove a cancer or make it smaller so that chemotherapy and radiation are more effective. Risks include anesthesia, bleeding problems, and postoperative pain. Cures are possible with certain cancers and early intervention.
  • Chemotherapy - Chemotherapy uses drugs to try to kill the cancer cells with the least amount of damage to normal cells. Side effects can include nausea, lowered immunity, and bleeding problems. Dogs don't usually experience major hair loss. Not all cancers are susceptible to chemotherapy.
  • Radiation - Radiation uses specially calibrated X-rays to damage cancer tissues with the least amount of damage possible to normal tissues. Side effects include tissue sloughing, lowered immunity, and damage to normal tissue. Anesthesia is required. This treatment is only available at veterinary referral centers. Not all cancers are susceptible to radiation and location of the cancer may make this impossible.
  • Cryotherapy - Cryotherapy uses probes to freeze cancerous tissues. The goal is to destroy the cancer with the least damage to surrounding normal tissues. This is only available at veterinary referral centers. Not all cancers are susceptible to cryotherapy, and the location of the cancer may make this therapy impossible.
  • Hyperthermy - Hyperthermy uses heat probes or radiation to destroy cancerous tissues by overheating them. The goal is to destroy the cancer with the least damage to surrounding normal tissues. This is only available at veterinary referral centers. Not all cancers are susceptible to heat damage. The location of the cancer may make this therapy impossible.
  • Diet - Diet has been shown to be helpful in controlling cancer. The goal is a diet with limited simple sugars, moderate amounts of complex sugars such as carbohydrates, highly digestible protein in moderate amounts, and set amounts of certain types of fats. These dietary guidelines tend to “starve” the cancer cells and help the normal cells stay healthy. There is a commercial cancer diet called n/d from Hill's, or you can make a homemade diet that fits these criteria.
  • Immunotherapy - Immunotherapy use immune reactions to fight off the cancer cells. This method may use a nonspecific immune modifier such as interferon, or vaccines specifically tailored to the cancer of the individual. Much of this work is experimental but shows great promise.

This article is excerpted from “Dog Owner’s Home Veterinary Handbook” with permission from Wiley Publishing, Inc.