Letrozole Superior to Tamoxifen After Breast Cancer Surgery, According to New Data

Newly published data in the August 20, 2009, issue of The New England Journal of Medicine affirm 5-year upfront use of letrozole (Femara) following surgery as an optimal treatment approach vs tamoxifen for postmenopausal women with early-stage breast cancer (hormone-receptor positive).

The data include an analysis from the Breast International Group (BIG) 1-98 trial that evaluated patients taking either a sequence of letrozole and tamoxifen for 5 years or letrozole as monotherapy for 5 years. Also included is the update of the Monotherapy Arms Analysis (MAA) conducted 10 years after initiation of the study, comparing 5 years of letrozole alone vs 5 years of tamoxifen alone following surgery (adjuvant setting). The BIG 1-98 trial was conducted by the International Breast Cancer Study Group (IBCSG).

Sequential Treatments Analysis
Results from the Sequential Treatments Analysis (STA) concluded that sequential treatment with tamoxifen and letrozole in the first 5 years after breast cancer surgery did not improve disease-free survival compared with letrozole alone for the same duration after surgery. In the 10-year MAA analysis, letrozole monotherapy demonstrated significant long-term improvement of disease-free survival (P = .03) and significant long-term reduction in risk of distant metastasis (P = .05) compared with tamoxifen. In patients treated with letrozole monotherapy, a nonstatistically significant relative reduction in the risk of death of 13% vs tamoxifen (P = .08) was observed.

“The BIG 1-98 study results suggest survival benefit with 5 years of letrozole therapy after surgery compared to tamoxifen for the same time period following surgery, confirming the benefit of initial use of letrozole in the adjuvant breast cancer setting,” said Henning T. Mouridsen, MD, PhD, professor of oncology, Copenhagen University Hospital and BIG 1-98 investigator. “Letrozole is the only aromatase inhibitor vs tamoxifen to demonstrate early and significant reduction in the risk of distant metastases, significant improvement in disease-free survival, and this suggestion in overall survival benefit in primary breast cancer patients.”

Kimberly Blackwell, MD, associate professor of medicine at the Duke University Medical Center, commented, “A primary goal in treating adjuvant breast cancer is to reduce the number of early, life-threatening distant metastases. The data show the significant long-term benefit of Femara and these results will have an impact on clinical practice in the US. A treatment strategy of letrozole for 5 years immediately following surgery may help protect postmenopausal women with hormone-receptor–positive breast cancer from recurrence of their disease.”