Oophorectomy and colon cancer. Impact on survival

Data on survival and survival free-from-recurrence were analyzed retrospectively in a group of 571 women who had undergone curative resection for colon cancer at the Mayo Clinic between 1972 and 1978. Of these women, 75 (group 1) had required bilateral oophorectomy before or at colon resection, while 496 (group 2) retained one or both ovaries. Average age, location and grade of tumor, and duration of follow-up were similar for both groups. Five-year-survival rate for the 571 women was 73.6%, as compared with 84.3% for matched controls. The 5-year survival rates were not significantly different for group 1 (78.0%) and group 2 (72.9%). Five-year survival free-from-recurrence also was not significantly different (82.9%, group 1 and 79.5%, group 2). Women in group 1 who had grade 1 or 2 tumors or lesions in the sigmoid and cecum fared the best (no significant difference from controls). Incidence studies of ovarian metastases from colon cancers suggest that three to eight per cent of women should benefit from bilateral oophorectomy. This agrees with the difference in survival observed between groups 1 and 2 in this study. Our sample size is too small to statistically confirm the reliability of this difference. The design of a prospective study testing this hypothesis is outlined.