The benefit from 5 years of tamoxifen therapy persists through 10 years of follow-up. No additional advantage is obtained from continuing tamoxifen therapy for more than 5 years.

Information is presented from 555 patients with Dukes B and C rectal cancers treated by curative resection who were entered into the National Surgical Adjuvant Breast and Bowel Project (NSABP) protocol R-01 between November 1977 and October 1986. Their average time on study was 64.1 months. The patients were randomized to receive no further treatment (184 patients), postoperative adjuvant chemotherapy with 5-fluorouracil, semustine, and vincristine (MOF) (187 patients), or postoperative radiation therapy (184 patients). The chemotherapy group, when compared with the group treated by surgery alone, demonstrated an overall improvement in disease-free survival (P = .006) and in survival (P = .05). Employing the proportional hazards model, a global test was used to determine the presence of treatment interactions. Investigation of stratification variables employed in this study indicated that sex, and to a lesser extent age and Dukes stage, made individual contributions to the disease-free survival and the survival benefit from chemotherapy. When evaluated according to sex, the benefit for chemotherapy at 5 years, both in disease-free survival (29% vs. 47%; P less than .001; relative odds, 2.00) and in survival (37% vs. 60%; P = .001; relative odds, 1.93), was restricted to males. When males were tested for age trend with the use of a logistic regression analysis, chemotherapy was found to be more advantageous in younger patients. When the group receiving post-operative radiation (4,600-4,700 rad in 26-27 fractions; 5,100-5,300 rad maximum at the perineum) was compared to the group treated only by surgery, there was an overall reduction in local-regional recurrence from 25% to 16% (P = .06). No significant benefit in overall disease-free survival (P = .4) or survival (P = .7) from the use of radiation has been demonstrated. The global test for interaction to identify heterogeneity of response to radiation within subsets of patients was not significant. In conclusion, this investigation has demonstrated a benefit from adjuvant chemotherapy (MOF) for the management of rectal cancer. The observed advantage was restricted to males. Postoperative radiation therapy reduced the incidence of local-regional recurrence, but it failed to affect overall disease-free survival and survival.

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Complications associated with small bowel intolerance to radiation therapy at doses higher than 4500 to 5000 cGy have been the limiting factor in delivering pelvic radiation either as an adjuvant to surgery or alone in the treatment of pelvic malignancies. Despite numerous surgical, medical, and radiation therapy technical measures to minimize small bowel injury, none have been uniformly successful in eliminating this problem. With the availability of a new synthetic absorbable mesh, a pelvic sling can be placed at the time of exploration or definitive surgery aimed at suspending the small bowel out of the pelvis. Preliminary work in animal models has shown the mesh sling to be well-tolerated and successful. Barium-contrast simulation studies of seven patients with pelvic malignancies requiring resectional surgery and postoperative radiation therapy in whom the mesh sling was placed at the time of surgery demonstrate total exclusion of the small bowel from the pelvic radiation treatment field. All patients have been followed for at least 4 months since mesh placement, and to date no complications have occurred. It is possible that this technique of bowel exclusion will permit the delivery of larger doses of radiation therapy in patients with pelvic malignancies aiming at more effective local and regional control of cancer without increased complications from radiation-associated small bowel injury.