Adjuvant radiation therapy for rectal adenocarcinoma.

Adjuvant pelvic radiation is intended to reduce the incidence of pelvic tumor recurrence and improve the survival rates of patients who have "curative" resections for adenocarcinoma of the rectum. The results of trials of preoperative radiation of up to 2500 cGy in two weeks have been disappointing. However, studies with preoperative or postoperative radiation doses of 4500 cGy in five weeks or more suggest that the risk of pelvic recurrence can be reduced to 15 per cent or less, although follow-up in most studies is too brief to allow any comment on changes in survival rates. These promising results need to be confirmed, since most were not obtained in appropriately controlled studies. Although these higher radiation doses do appear to be safe when attention is paid to surgical and radiotherapy techniques, this also needs to be confirmed with larger numbers of patients and longer follow-up. While the studies suggest that higher radiation doses are more effective than lower doses, there is no agreement on whether radiation should be directed to the region of the primary tumor only, or also to the pelvic lymph nodes, nor whether radiation should be given before or after surgery. Although the use of adjuvant pelvic radiation is becoming more widespread, these and other questions need to be answered before adjuvant radiation can be considered standard therapy.