Study Comparing Lasofoxifene Plus Abemaciclib to Fulvestrant Plus Abemaciclib in Adults With Advanced or Metastatic ERHER2- Breast Cancer Having ESR1 Mutation

What this Trial Is About

Researchers are evaluating the combination of lasofoxifene and abemaciclib compared to fulvestrant and abemaciclib for treating pre- and postmenopausal women and men with locally advanced or metastatic estrogen receptor positive ERhuman epidermal growth factor 2 negative HER2- breast cancer who have an ESR1 mutation and have previously been treated with ribociclib or palbociclib. The study aims to compare the effectiveness, safety, and tolerability of these two treatment combinations. Participants are randomly assigned to one of two groups one receives 5 mg daily oral lasofoxifene plus oral abemaciclib 150 mg twice a day the other receives fulvestrant 500 mg via intramuscular injections on Days 1, 15, and 29 and then monthly thereafter, combined with oral abemaciclib 150 mg twice a day. This open-label study assesses these treatments over approximately three years. During the trial, participants will be monitored through regular assessments including tumor measurements, survival tracking, quality of life questionnaires, and evaluation of adverse events. Researchers will measure progression-free survival as the primary outcome and also track response rates, overall survival, treatment duration, and time to chemotherapy. Brain metastases patients meeting specific criteria are allowed, and safety is closely observed throughout the study period which may last up to about three years.

Evaluation of Lasofoxifene Combined With Abemaciclib Compared With Fulvestrant Combined With Abemaciclib in Locally Advanced or Metastatic ER+/HER2- Breast Cancer With an ESR1 Mutation