Breast Cancer Coverage from Every Angle

10-Year Findings With Letrozole in Hormone Receptor–Positive Breast Cancer

By: Lauren Harrison, MS
Posted: Wednesday, February 12, 2020

Patients with hormone receptor–positive breast cancer experienced improvements in breast cancer–free interval, distant recurrences, and disease-free survival when receiving extended adjuvant endocrine therapy with letrozole, but no significant improvement in overall survival was reported. Eleftherios P. Mamounas, MD, of the Orlando Health UF Health Cancer Center in Florida, presented the results of the NRG Oncology/NSABP B-42 trial on behalf of his colleagues at the San Antonio Breast Cancer Symposium (Abstract GS4-01).

This trial included 3,966 postmenopausal women with stage I to III hormone receptor–positive breast cancer who were free of disease after either 5 years on an aromatase inhibitor or tamoxifen followed by an aromatase inhibitor for 5 years. Patients were randomly assigned to receive letrozole or placebo daily for an additional 5 years.

At a median follow-up of 9.3 years, there were 890 disease-free events. Treatment with letrozole yielded a statistically significant increase in disease-free survival compared with placebo (hazard ratio = 0.84), and the 10-year disease-free survival was 76.1% compared with 72.1% for placebo. There were 495 deaths recorded during this study, with no significant difference in overall survival between letrozole and placebo. There were 413 breast cancer free–interval events recorded, and patients treated with letrozole had a statistically significant 26% decrease in breast cancer free–interval events. There was also a 29% decrease in disease recurrence in patients treated with letrozole. The 10-year cumulative incidence of disease recurrence with letrozole was 5.7%, compared with 7.5% with placebo. There was no significant difference in the time to osteoporotic fractures, nor was there a significant increase in arterial thrombotic events with letrozole compared with placebo.

Disclosure: For full disclosures of the study authors, visit

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