Purpose: Postmenopausal estrogen use has been shown to decrease the incidence of colorectal cancer, but there is limited information regarding the effect of estrogen use on survival after diagnosis of colorectal cancer.
Participants and methods: We examined the influence of postmenopausal estrogen use on mortality among 834 women participating in the Nurses' Health Study who were diagnosed with colorectal cancer between 1976 and 2000 and observed until death or June 2004, whichever came first. Colorectal cancer-specific mortality and overall mortality according to categories of hormone use were assessed. Cox proportional hazards models were used to calculate hazard ratios (HRs) adjusted for other risk factors for cancer survival.
Results: Postmenopausal estrogen use before diagnosis of colorectal cancer was associated with significant reduction in mortality. Compared with women with no prior estrogen use, those reporting current use before diagnosis had an adjusted HR of 0.64 (95% CI, 0.47 to 0.88) for colorectal cancer-specific mortality and 0.74 (95% CI, 0.56 to 0.97) for overall mortality. This inverse association between hormone use and mortality was most evident among women whose duration of use was less than 5 years. Longer durations and past use were not associated with significant survival benefit. Assessment of estrogen use after diagnosis demonstrated similar findings.
Conclusion: Current postmenopausal estrogen use before diagnosis of colorectal cancer was associated with improved colorectal cancer-specific and overall mortality. This benefit was principally limited to women who initiated estrogens within 5 years of diagnosis. Additional efforts to understand mechanisms through which estrogens influence colorectal carcinogenesis and cancer progression seem warranted.