Breast cancer diagnosed during hormone replacement therapy

Objective: Hormone replacement therapy (HRT) is associated with decreased breast cancer mortality despite increased incidence. We studied postmenopausal breast cancer patients to determine whether this paradox results from earlier diagnosis, biologically less aggressive tumors, or cessation of hormonal stimulation. Methods: Demographic, clinical, pathologic, treatment, and outcome information for 455 postmenopausal breast cancer patients who had not used postmenopausal hormones was compared with that of 47 breast cancer patients who used postmenopausal hormones prior to diagnosis. Results: Hormone users were significantly younger, more often white, and of lower body mass index than nonusers. Hormone users presented significantly more often with nonpalpable mammographic findings, resulting in significantly smaller tumors with less nodal involvement than nonusers. Cancers of hormone users were more commonly invasive lobular or in situ ductal and were more likely to be steroid receptor positive. Hormone users were treated with breast conservation significantly more frequently than nonusers. These differences persisted after matching for age and year of surgery and after controlling for race. At 5 years, none of the hormone users with invasive cancers had local recurrence compared with 8% of nonusers, and 7% of users had distant disease compared with 10% of nonusers. Conclusion: These results indicate that favorable breast cancer survival after postmenopausal hormone use might result from earlier detection through mammography. Possible hormonal influence on tumor biology and prognosis was not supported by our data. (C) 2000 by The American College of Obstetricians and Gynecologists.