The importance of optimal treatment planning in radiation therapy.

There are two classes of failure in radiation therapy: local control not achieved and radiation-induced morbidity. Technical developments which permit the employment of treatment volumes which achieve a closer approximation to the target volume can confidently be asserted to yield clinical gains in terms of higher tumor control rates and/or reduced severity/frequency of radiation induced morbidity. The magnitude of the gains and the cost and effort to realize those gains may need to be assessed by the technique of the "clinical trial." Such gains will be the consequence of a higher dose to the target and/or the irradiation of smaller volumes of non-target tissues. An important fact is that unirradiated tissues do not develop radiation-related injury. Selected categories of radiation injuries that appear in non-target tissues are here reviewed. Valuable advances in the technology of radiation therapy are virtually certain for the near term. This bodes well, indeed, for our future patients.