Breast cancer diagnosed during hormone replacement therapy

Objective: Hormone replacement therapy (HRT) is associated with decreased b reast cancer mortality despite increased incidence. We studied postmenopaus al breast cancer patients to determine whether this paradox results from ea rlier diagnosis, biologically less aggressive tumors, or cessation of hormo nal stimulation. Methods: Demographic, clinical, pathologic, treatment, and outcome informat ion for 455 postmenopausal breast cancer patients who had not used postmeno pausal hormones was compared with that of 47 breast cancer patients who use d 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 significan tly smaller tumors with less nodal involvement than nonusers. Cancers of ho rmone users were more commonly invasive lobular or in situ ductal and were more likely to be steroid receptor positive. Hormone users were treated wit h breast conservation significantly more frequently than nonusers. These di fferences persisted after matching for age and year of surgery and after co ntrolling for race. At 5 years, none of the hormone users with invasive can cers 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 af ter 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 Obstetricia ns and Gynecologists.