Use of hormone replacement therapy and the risk of colorectal cancer.

PURPOSE: Estrogen/progestin replacement therapy is prescribed to women in menopause for purposes of postmenopausal symptom control or prevention of hormone deficiency-related diseases such as osteoporosis. Such treatments have formerly been shown to be associated with lower colorectal cancer risk in an as yet unknown mechanism. PATIENTS AND METHODS: The Molecular Epidemiology of Colorectal Cancer study was a population-based case-control study in northern Israel of patients with colorectal cancer who were diagnosed between 1998 and 2006, and age-, sex-, clinic-, and ethnicity-matched population controls. Use of hormone replacement therapy (HRT) was assessed using a structured interview and validated by studying prescription records in a subset of patients for whom they were available.
RESULTS: Two thousand four hundred sixty peri/postmenopausal women were studied from among 2,648 patients with colorectal cancer and 2,566 controls. The self-reported use of HRT was associated with a significantly reduced relative risk of colorectal cancer (odds ratio [OR], 0.67; 95% CI, 0.51 to 0.89). This association remained significant after adjustment for age, sex, use of aspirin and statins, sports activity, family history of colorectal cancer, ethnic group, and level of vegetable consumption (OR, 0.37; 95% CI, 0.22 to 0.62). Statistically significant interactions were seen between use of HRT and use of aspirin and involvement in sports activity. Using pharmacy data, only users of combined oral preparations demonstrated a significant negative association with colorectal cancer.
CONCLUSION: The use of oral HRT was associated with a 63% relative reduction in the risk of colorectal cancer in postmenopausal women after adjustment for other known risk factors. This effect was not found in aspirin users and women with intensive sports participation.