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Extended Letrozole Therapy After Aromatase Inhibitor–Based Therapy in Breast Cancer

By: Melissa E. Fryman, MS
Posted: Tuesday, March 5, 2019

According to the results from the NRG Oncology/NSABP B-42 trial, 5 years of letrozole therapy after 5 years of prior aromatase inhibitor–based therapy did not significantly improve disease-free survival for postmenopausal women with hormone receptor–positive breast cancer. However, the rate of distant recurrence events was reduced with letrozole, particularly after 4.1 years. Eleftherios P. Mamounas, MD, of the University of Florida Health Cancer Center at Orlando Health, and colleagues published these findings in The Lancet Oncology.

“Our findings suggest that careful assessment of the risks and potential benefits of extended letrozole therapy is required before recommending this treatment to any patients with early-stage breast cancer,” concluded the authors.

In this phase III, international, double-blinded study, 3,966 postmenopausal women with stages I to IIIA hormone receptor–positive breast cancer were randomly assigned to receive letrozole or placebo. Of these patients, 3,903 (1,950 receiving letrozole, and 1,953 receiving placebo) were analyzed for disease-free survival, with a 2-tailed significance level prespecified at .0418. Disease-free survival was defined as the time from randomization to breast cancer recurrence, second primary malignancy, or death.

After a median follow-up of 6.9 years, no significant difference in disease-free survival was seen between the letrozole and placebo groups (292 and 339 disease-free survival events, respectively, P = .048). The estimated 7-year disease-free survival was 84.7% versus 81.3%, respectively. The most common grade 3 adverse events were joint and back pain (in both groups); the most common grade 4 adverse events were thromboembolic events (placebo group) and urinary tract infection, hypokalemia, and left ventricular systolic dysfunction (letrozole group).

Disclosure: The study authors’ disclosure information may be found at thelancet.com.



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