Dr. Goetz on the ELAINE-1 Trial of Lasofoxifene in ESR1-Mutated, ER+/HER2- Breast Cancer

Matthew P. Goetz, MD, consultant, Division of Medical Oncology, Department of Oncology, Mayo Clinic, discusses the progression-free survival (PFS) benefit derived with lasofoxifene in patients with ESR1-mutated, estrogen receptor (ER)–positive/HER2-negative metastatic breast cancer.

The phase 2 ELAINE-1 trial (NCT03781063) compared the safety and efficacy of lasofoxifene with that of fulvestrant (Faslodex) in this patient population. Enrolled patients were required to have experienced disease progression on an aromatase inhibitor and a CDK4/6 inhibitor, Goetz says. Participants were randomly assigned to receive oral lasofoxifene at 5 mg daily or 500 mg of fulvestrant administered intramuscularly on days 1, 15, and 29, and every 4 weeks thereafter, Goetz adds.

Data presented at the 2022 ESMO Congress showed that treatment with lasofoxifene (n = 52) resulted in a median PFS of 6.04 months (95% CI, 2.82-8.04) compared with 4.04 months (95% CI, 2.93-6.04) with fulvestrant (n = 51; HR, 0.699; 95% CI, 0.445-1.125; P= .138). Although it was not determined to be statistically significant, the difference in median PFS was a positive signal, and there was clear evidence of antitumor activity with lasofoxifene in this population, Goetz concludes.