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Letrozole not superior to anastrozole for breast cancer in postmenopausal women
Letrozole did not show significant superiority or improved safety for postmenopausal women with hormone receptor–positive, node-positive early-stage breast cancer compared with anastrozole, a phase 3 trial found.
“Both letrozole and anastrozole have been shown to have superior efficacy compared with tamoxifen,” Ian Smith, MD, of The Royal Marsden Hospital and Institute of Cancer Research in Surrey, United Kingdom, and colleagues wrote. “Published data have indicated that the relative benefit of both agents varies across patient subgroups, and, in particular, an exploratory analysis of the BIG 1-98 trial showed that patients with node-positive disease seemed to derive a greater benefit versus tamoxifen than did patients with node-negative disease. Hence, it was believed that there was an unmet need, first, to assess head-to-head the relative efficacy of these two nonsteroidal aromatase inhibitors and, second, to evaluate their benefit in higher-risk patients with node-positive disease.”
Researchers randomly assigned 4,136 postmenopausal women with hormone receptor–positive, node-positive early-stage breast cancer to either letrozole (n = 2,061) or anastrozole (n = 2,075).
Five-year DFS was 84.9% for patients assigned letrozole compared with 82.9% among those assigned anastrozole (HR = 0.93; 95% CI, 0.8-1.07). Exploratory analysis showed similar DFS with both drugs among all evaluated subgroups.
Five-year OS was 89.9% for the letrozole arm compared with 89.2% in the anastrozole arm (HR = 0.98; 95% CI, 0.82-1.17).
The most common grade 3 or 4 adverse events — those that occurred in more than 5% of patients — were arthralgia (letrozole, 3.9% vs. anastrozole, 3.3%), hypertension (1.2% vs. 1%), hot flushes (0.8% vs. 0.4%), myalgia (0.8% vs. 0.7%), dyspnea (0.8% vs. 0.5%) and depression (0.8% vs. 0.6%).
“Letrozole did not provide statistically superior efficacy over anastrozole in either the primary endpoint of DFS or the secondary endpoint of OS,” the researchers wrote. “No new safety concerns were identified, and there were no unexpected short-term or long-term treatment-related toxicities in either of the treatment arms. The study was terminated prematurely because of lower-than-expected DFS events, and the data presented here are based on the final analysis of 709 DFS events. Primary breast cancer tissue, blood and germline single nucleotide polymorphism biomarker analyses are … ongoing.” – by Andy Polhamus
Disclosure: Smith reports honoraria from Eisai and Seattle Genetics, as well as consulting or advisory roles with Pierre Fabre. Please see the study for a full list of all other researchers’ relevant financial disclosures.