Normal tissue tolerance and management of radiation injury

The objective of effective cancer therapy includes preservation of normal tissue function and reducing injury as much as possible. Acutely responding tissues such as skin and mucous membranes generally show a reaction during the course of radiation therapy. Normally those reactions heal rapidly after radiation therapy is completed. The short-term injury is justified if a reasonable probability of local tumor control is expected with an increase in survival of several months. Late effects are more challenging to manage and, therefore, the probability of occurrence is reduced by the methods of irradiation. If the tumor is located such that eyes or salivary glands are included in the field, the late effects include keratoconjunctivitis sicca and, less frequently, xerostomia. Those responses require continual observation and care by the animal owner. A goal in radiation therapy is to keep the incidence of serious complications such as bone or soft-tissue necrosis below 5%. The incidence of complications of radiation therapy that have serious impact on quality of life or quality as a companion animal is probably much less than 5%.