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No significant improvement in overall survival was noted in patients with early-stage, HER2-positive breast cancer treated with neratinib compared with placebo, according to results of the ExteNET study (Clinical Trials.gov Identifier: NCT00878709) presented at the 17th St. Gallen International Breast Cancer Conference 2021.
However, there are data to indicate that neratinib was associated with improved overall survival among patients with hormone receptor (HR)-positive disease, with a trend toward improved central nervous system (CNS) outcomes in patients with early-stage HER2-positive disease.
Miguel Martin, of Instituto de Investigacion Sanitaria Gregorio Maranon, Madrid Spain, and colleagues presented data from the randomized, phase 3 trial that included 2840 patients with early-stage, HER2-positive breast cancer. Patients were randomly assigned to oral neratinib 240 mg/d or placebo for 1 year. Median duration of follow-up for overall survival was 8.1 years.
Previously presented data showed an absolute invasive disease-free survival benefit of 2.5% and a distant disease-free survival benefit of 1.7% with neratinib compared with placebo.
In the poster, the researchers presented final overall survival data. In the intent-to-treat population, the estimated 8-year overall survival was 90.1% with neratinib and 90.2% with placebo. In HR-positive disease, estimated 8-year overall survival was 91.6% with neratinib compared with 90.1% with placebo (HR=0.80; 95% CI, 0.58-1.12). In HR-negative disease, neratinib did not improve overall survival (88.1% vs. 90.3%; HR-1.18; 95% CI, 0.83-1.69).
Among patients with HR-positive disease who initiated treatment within 1 year of completing trastuzumab, the estimated 8-year overall survival was 91.5% with neratinib compared with 89.4% with placebo, reflecting a 2.1% absolute benefit (HR=0.79; 95% CI, 0.55-1.13).
More specifically, in this group of patients with no pathologic complete response, 8-year overall survival was 91.3% with neratinib compared with 82.2% with placebo, reflecting a 9.1% absolute benefit. In patients with a pathologic complete response, 8-year overall survival was 93.3% with neratinib compared with 73.7% with placebo, reflecting a 19.6% absolute benefit.
The researchers also looked at CNS outcomes. Among patients with HR-positive disease who initiated treatment within a year of trastuzumab, neratinib was associated with a lower number of CNS events across all groups studied. According to the researchers, “neratinib is the first HER2-directed agent to show a trend towards improved CNS outcomes in early stage HER2-positive breast cancer.”
Disclosure: Some authors declared affiliations with and receipt of funding from the pharmaceutical industry. Please refer to the original article for a full list of disclosures.
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Martin M, Holmes FA, Moy B, et al; on behalf of the ExteNET Investigators. Continued efficacy of neratinib in patients with HER2-positive (HER2+) early-stage breast cancer: final overall survival (OS) analysis from the randomized phase 3 ExteNET trial. Poster presentation at: 17th St. Gallen International Breast Cancer Symposium 2021; March 17-21, 2021. Abstract P005.