Breast cancer survival and hormone replacement therapy: a cohort analysis

Controversy exists regarding the safety of hormone replacement therapy (HRT) after a diagnosis of breast cancer. The objective of this study is to perform a matched cohort analysis to evaluate the impact of HRT on mortality in breast cancer survivors. Patients with breast cancer who received HRT after diagnosis of breast cancer were identified. Control subjects were identified from the regional cancer registry. Matching criteria included age at diagnosis, stage of breast cancer, and year of diagnosis. Controls were selected only if they were alive at the time of initiation of HRT of the matched case. Only subjects not included in a previously reported matched analysis were selected. One hundred twenty-five cases were matched with 362 controls. Ninety-eight percent (123/125) of the cases received systemic estrogen; 90/125 (72%) also received a progestational agent. The median interval between diagnosis of breast cancer and initiation of HRT was 46 months (range 0-401 months). The median duration of HRT was 22 months (range 1-357 months). The risk of death was lower among the HRT survivors; odds ratio 0.28 (95% confidence interval 0.11-0.71). This analysis does not suggest that HRT after the treatment of breast cancer is associated with an adverse outcome.