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.
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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
- 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.
