Letrozole Does Not Offer Better Survival, Safety Than Anastrozole in Breast Cancer

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Letrozole and anastrozole have similar survival efficacy and safety profiles in hormone receptor-positive, node-positive breast cancer.
Letrozole and anastrozole have similar survival efficacy and safety profiles in hormone receptor-positive, node-positive breast cancer.

SAN ANTONIO— Letrozole and anastrozole have similar survival efficacy and safety profiles in postmenopausal patients with hormone receptor-positive (HR+), node-positive breast cancer, according to the final efficacy and safety analysis of data from a randomized phase 3 multicenter study presented at the 2015 San Antonio Breast Cancer Symposium.1

“Treatment with letrozole did not demonstrate superior efficacy over anastrozole in postmenopausal patients with HR+ and lymph node-positive early breast cancer,” reported lead author Joyce O'Shaughnessy, MD, of the Baylor Charles A. Sammons Cancer Center in Dallas, TX.

“Disease-free survival and overall survival were not statistically different between treatment arms, both overall and across all subgroups evaluated,” she noted.

Nearly 80% of breast cancers are HR+, and aromatase inhibitors are “the cornerstone of treatment for postmenopausal women with estrogen-receptor-positive (ER+) breast cancer,” Dr O'Shaughnessy reported. However, until now, there have been no head-to-head trial data comparing the 2 approved nonsteroidal aromatase inhibitors for this patient population, letrozole and anastrozole. 

The letrozole (Femara) vs Anastrozole Clinical Evaluation study (FACE; NCT00248170) enrolled a total of 4136 postmenopausal women with HR+ and lymph-node positive breast cancer between December 2005 and March 2008, and randomly assigned to receive either letrozole (2.5 mg daily; 2061 patients) or anastrozole (1 mg daily; 2075 patients) for 5 years in the adjuvant setting, Dr O'Shaughnessy said.

“Patients were stratified by the number of positive lymph nodes (1-3 versus 4+) and HER2 status (positive versus negative or unknown),” she explained. 

Treatment continued for 5 years or until disease recurrence, she said. The primary endpoint was disease-free survival (DFS) at 5 years.

“The study was terminated early (on September 8, 2014) because the observed event rate and number of patients continuing to be followed-up would require follow-up to the year 2022,” Dr O'Shaughnessy explained.

The estimated 5-year disease-free survival rates were 84.9% for letrozole vs 82.9% for anastrozole (hazard ratio [HR] 0.93; 95% CI: 0.80-1.07]; P = .3150, not significant). Overall survival (OS) “was not statistically different between arms (HR 0.98; 95% CI: 0.82-1.17]; P = .7916),” Dr O'Shaughnessy reported.

“Primary reasons for treatment discontinuation in the letrozole vs anastrozole arms were adverse events (AEs: 15.1% vs 14.3%) and disease progression (9.5% vs 10.4%),” Dr O'Shaughnessy reported.

Safety profiles were “similar between treatment arms,” she noted. “The most common AEs in the letrozole versus anastrozole arms were arthralgia (48.2% vs 47.9%), hot flushes (32.5% vs 32.3%) and fatigue (16.8% vs 16.6%). Suspected drug-related grade 3/4 AEs were reported in 9.5% of patients in the letrozole arm versus 8.1% of patients in the anastrozole arm.”

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Suspected drug-related AEs that led to treatment discontinuation occurred in 14.0% vs 12.9% of patients in letrozole vs anastrozole arms.

Primary tumor tissue, blood and germline single nucleotide polymorphism (SNP) biomarker analyses are “ongoing,” she reported.

Reference

  1. O'Shaughnessy J, Yardley DA, Burris HA, et al. Randomized phase 3 trial of adjuvant letrozole versus anastrozole in postmenopausal patients with hormone receptor positive, node positive early breast cancer: final efficacy and safety results of the femara versus anastrozole clinical evaluation (Face) trial. Oral presentation at: San Antonio Breast Cancer Symposium 2015; December 9, 2015; San Antonio, TX.

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