What Are the Dose-Volume Constraints to Reduce Late Toxicity?
A reduction of the risk of late postradiation toxicity is a key issue in the current debate on the indications for preoperative radiotherapy. The objective of this chapter is to provide readers with a proposal of modifying currently recommended clinical target volume (CTV) boundaries in order to diminish the risk of postradiation late side effects. Preoperative radiation increases slightly the risk of non-cancer death and the risk of small bowel obstruction. Lowering cranial border of the CTV to the S2–S3 interface may reduce this toxicity. Preoperative radiation increases the risk of anorectal and sexual function impairment in patients undergoing anterior resection and the risk of perineal wound healing delay in patients undergoing abdomino-perineal resection. Adequate location of the caudal border of the CTV may reduce this toxicity. The sphincters’ complex, the caudal part of the vagina, the penile bulb and the perineal skin should be avoided in CTV delineation, provided these regions are not invaded by a distal cancer extension. Examples of CTV contouring are provided.
KeywordsClinical Target Volume Preoperative Radiation Circumferential Resection Margin Ischiorectal Fossa Perineal Skin
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