The role of preoperative and postoperative radiotherapy in rectal cancer.

Radiotherapy has an important role to play when used in addition to surgery in primary and recurrent rectal cancer. In primary resectable rectal cancer, a large number of randomized trials have shown that preoperative radiotherapy can slightly improve survival and can decrease local recurrence rates by more than half. Postoperative radiotherapy may also decrease the risk of local failure although with less efficacy. A preoperative schedule of 5 Gy/day for 5 out of 7 days is a convenient and low-toxic treatment, provided it is not given with 2 beams to large volumes, and it appears to be at least as effective as postoperative radiochemotherapy, generally meaning 6 months of therapy with 5 weeks of radiation. The schedule of 5 Gy/day for 5 days also reduces local recurrences with total mesorectal excision. It is unlikely that preoperative radiochemotherapy will substantially increase the chances of a sphincter-preserving procedure in a low-lying rectal cancer and that the long-term function will be adequate even if this is believed by many. In primary nonresectable or locally recurrent rectal cancer, preoperative radiotherapy may downsize or downstage the tumor so that it can be resected. Scientific support that radiochemotherapy is more efficient than radiotherapy alone in this situation is weak.