Risk of breast cancer in post-menopausal women using hormone replacement therapy.

To study the relationship of hormone replacement therapy (HRT) in post-menopausal women and risk of breast cancer.The authors conducted a case-control study comparing the proportion of HRT used between breast cancer and non-breast-cancer women. Cases were breast cancer patients who had natural menopause (excluded hysterectomy) and aged > or = 50-years-old from the Siriraj Breast Cancer database (1983-1996). Controls were post-menopausal volunteers aged 50 year or older who visited Siriraj Hospital for other purposes such as elderly clinics, health check, etc. After informed consent, well-trained surgeons examined the women in the control group to exclude any potential breast cancer. Patient characteristics and risk factors were collected.Of 1,913 patients in the database, 623 were included as the cases. Data from 679 volunteers were collected for controls from May to December 1999. Among 1,302 of the study population 58 women had ever used HRT (4.5%), which distributed to 3.2 per cent (20/623) in cases and 5.6 per cent (38/679) in controls. From univariate analysis, age, age at menopause, number of children, habitat, education, contraceptive pills, familial history of breast cancer and HRT usage were associated with breast cancer (p-value<0.05). After multivariate forward stepwise logistic regression analysis, there was no association between HRT use and breast cancer (adjusted odds ratio (OR) = 0.61, 95% CI = 0.31-1.20). In subgroups analysis, women who had older age, higher education level, history of taking contraceptive pills, or positive familial history of breast cancer in second degree relatives had a decreased risk of breast cancer, while those living outside Bangkok had an increased risk.Hormonal replacement therapy in post-menopausal women was not associated with increased risk of breast cancer.