THURSDAY, Dec. 12, 2024 (HealthDay News) — For patients with estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer, imlunestrant leads to significantly longer progression-free survival among those with ESR1 mutations, according to a study published online Dec. 11 in the New England Journal of Medicine to coincide with the annual San Antonio Breast Cancer Symposium, held from Dec. 10 to 13 in San Antonio.
Komal L. Jhaveri, M.D., from the Memorial Sloan Kettering Cancer Center in New York City, and colleagues conducted a phase 3 trial enrolling 874 patients with ER-positive, HER2-negative advanced breast cancer that recurred or progressed during or after aromatase inhibitor therapy, administered alone or with a cyclin-dependent kinase 4 and 6 inhibitor. Patients were randomly assigned to receive imlunestrant, standard endocrine monotherapy, or imlunestrant-abemaciclib (331, 330, and 213 patients, respectively). Investigator-assessed progression-free survival was compared for imlunestrant versus standard therapy among 256 patients with ESR1 mutations and among all patients.
The researchers found that among the 256 patients with ESR1 mutations, median progression-free survival was 5.5 and 3.8 months with imlunestrant and standard therapy, respectively. The corresponding estimated restricted mean survival time was 7.9 and 5.4 months at 19.4 months. In the overall population, median progression-free survival was 5.6 and 5.5 months with imlunestrant and standard therapy, respectively (hazard ratio for progression or death, 0.87; 95 percent confidence interval, 0.72 to 1.04; P = 0.12). Comparing imlunestrant-abemaciclib with imlunestrant, median progression-free survival was 9.4 and 5.5 months, respectively (hazard ratio for progression or death, 0.57; 95 percent confidence interval, 0.44 to 0.73; P < 0.001).
“Imlunestrant therapy significantly improved progression-free survival over standard therapy among patients with ESR1 mutations,” the authors write.
Several authors disclosed ties to pharmaceutical companies, including Eli Lilly, which manufactures imlunestrant and funded the study.
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