Breast tumor characteristics in hormone replacement therapy users.

The aim of this study was to further elucidate the influence of HRT use, regarding duration, regimen and route of administration, on breast tumor characteristics. We evaluated the associations between HRT use and breast tumor characteristics in 530 postmenopausal women diagnosed with invasive breast cancer. Detailed information on HRT use and mammographic attendance were collected through a postal questionnaire. Adjusted odds ratios and 95% confidence intervals were calculated using logistic regression. Tumors in HRT users were significantly smaller, more often of ductal histologic type and with lower grade and lower mitotic index compared to tumors in nonusers. Tumor characteristics did not vary significantly by HRT duration, regimen and route of administration, except for mitotic index, which was more often of score 2 in long-term users, and of score 3 in short-term users. Higher mammographic surveillance among HRT users did not explain our results. We conclude that tumors in HRT users have a more favorable prognostic profile regardless of duration, regimen and route of administration. These effects seem to be due to the influence of HRT on preexisting tumors causing their greater differentiation rather than earlier detection due to mammographic surveillance.