This clinical trial is focused on studying a type of breast cancer known as estrogen receptor-positive/human epidermal growth factor receptor 2-negative (ER+/HER2-) breast cancer. This specific type of cancer has a mutation called ESR1 and has progressed despite previous treatments with hormone therapy and medications called CDK4/6 inhibitors. The study aims to compare the effectiveness of a combination of two medications, elacestrant and everolimus, against elacestrant alone. Elacestrant is a medication that targets hormone receptors, while everolimus is used to slow down the growth of cancer cells. The study will also include a group receiving a placebo, which is a substance with no active medication, to help understand the effects of the treatment.

Participants in the study will be randomly assigned to receive either the combination of elacestrant and everolimus, elacestrant with a placebo, or another treatment as part of the study. The study will be conducted in a way that neither the participants nor the researchers know which treatment each participant is receiving, a method known as “double-blind.” This helps ensure that the results are not influenced by expectations about the treatment. The main goal is to see if the combination of elacestrant and everolimus can help patients live longer without their cancer getting worse, which is referred to as “progression-free survival.”

The study will take place over several years, with regular check-ups and assessments to monitor the participants’ health and the progression of their cancer. Participants will receive their assigned treatment for a set period, and their response to the treatment will be closely monitored through various tests and evaluations. The study will also look at the overall survival of participants, the response of the cancer to the treatment, and any side effects experienced. This research is important for understanding how to better treat this specific type of breast cancer and improve outcomes for patients in the future.