A prospective study of menopausal hormones and risk of colorectal cancer (United States)

The relation of colorectal cancer and its subsites with use ofmenopausal hormones was evaluated in the United States among 40,464postmenopausal women, 41 to 80 years of age, who initially volunteered for anationwide breast-cancer screening program and were followed for an averageof 7.7 years. Ever-use of menopausal hormones was not associated with risk oftotal colorectal cancers (relative risk [RR] = 0.99, 95 percent confidenceinterval [CI] = 0.79-1.2) or cancers of the colon (RR = 1.1, CI = 0.81-1.6)or rectum (RR = 1.1, CI = 0.59-1.9). Recent hormone users, however, had asmall nonsignificant reduction in risk of colorectal cancer (RR = 0.78, CI =0.55-1.1), which was most pronounced for distal colon (RR = 0.68, CI =0.29-1.6) and rectal tumors (RR = 0.64, CI = 0.24-1.7). No effect wasobserved for former hormone users, and risk generally did not vary by timesince last use, type of regimen, or duration of use. However, the reducedrisk for recent users was stronger for users of five or more years'duration. These data show some lowering of colorectal cancer risk amongrecent menopausal hormone users of long duration.