Cancer Therapies

Treatment Side Effects

Please see the description of each of the types of cancer treatment for more details. In general, cancer treatment is tolerated well by dogs and cats.

Side effects of chemotherapy include nausea, vomiting, diarrhea, low cell counts and secondary infections, as well as a number of side effects unique to each of several drugs. These can be prevented or minimized in many patients with medication such as anti-nausea medication. Dogs and cats typically do not lose their hair but can have poor regrowth of hair in shaved areas. Dogs with continuously growing hair coats such as poodles can lose their hair and cats often lose their whiskers.

Radiation therapy affects only the tissues in the treatment field surrounding the tumor. Side effects happen either right away (acute) and start during treatment then continue for 2-4 weeks until healed, or they occur much later (chronic, 1-3 years) if the tissue does not change very rapidly such as nerves and bone. Most if not all pets will get some degree of acute side effects and all will heal, but very few patients experience chronic side effects which do not heal. Some chronic side effects such as damaged bone can be resolved with surgery. For acute side effects, we are very proactive about pain medication if needed. For dogs, a moist desquamation will occur on the skin if the tumor is or was near the surface of the skin. This is when the skin becomes scabbed and moist, red and thick. In cats, this is typically a dry flaky response.

Side effects of surgery include bleeding, infection, and poor healing. When tumors are removed from normal tissue, sometimes tumor cells that we can’t see are left behind and do not allow the tissue to heal. Sometimes the extent of surgery needed to fully remove a tumor leaves a great deal of tension on the remaining tissue, increasing the risk that the incision may reopen as it is trying to heal.

Side effects of photodynamic therapy include sloughing of the treated tissue as it is damaged and dies from the treatment. Sensitivity to the sun can persist for a few weeks following treatment, predisposing patients to sunburn.