Radiochemotherapy as an adjuvant treatment for rectal cancer.

Adjuvant treatment with radiotherapy has been proposed in rectal cancer surgery, due to the high local recurrence rate. However, the rate varies substantially in the literature, an this may be one reason that adjuvant treatment is not obvious to all surgeons. The difference may be due to selection bias, different criteria for curative surgery, different follow-up routines, and/or the skill of the surgeon. The data are unequivocal from all randomized trials comparing surgery alone with surgery plus radiotherapy, given either pre- or postoperatively: the average local recurrence rate is about 29% in the surgery-alone arm. With pre- or postoperative radiotherapy the local recurrence rate is more or less halved. Moreover, preoperative irradiation is more dose efficient than postoperative irradiation, indicating that a higher dose must be used when postoperative radiotherapy is delivered, with an increased risk of damaging the normal surrounding tissues in the pelvis. This damage of normal tissue also has an impact on sphincter function and on postoperative small bowel obstruction. Since preoperative radiotherapy is more effective in killing tumor cells at a lower dose than postoperative treatment with or without chemotherapy, and since preoperative treatment is less toxic to normal tissues, preoperative radiotherapy should be used whenever radiotherapy for rectal cancer is considered.