Rectal dose constraints for intensity modulated radiation therapy of the prostate.

Prostate dose escalation appears to have resulted in increased cancer control. Such escalation has been made possible by the ability to deliver more conformal treatment that spares normal tissue from the higher radiation doses. The supposition is that this has enabled higher doses, but without an increase in toxicity. The most disabling toxicity in prostate cancer radiotherapy is rectal. We evaluated the current status of conformal radiation and late rectal toxicity with the goal of determining whether reasonable rectal dose and volume constraints can be determined. Although the literature is inexact, we believe that some generalized constraints can be recommended and show that those recommendations are consistent with what is being used at experienced centers.