What the trial was testing
The monarchE Trial enrolled 5,637 patients with breast cancer. The study was sponsored by Eli Lilly and tracked outcomes across the full group of patients who matched the trial's eligibility profile.
It was a large trial designed to confirm whether the treatment works well enough for wider use. Trials at this stage are designed to produce evidence regulators and physicians can act on — not just observations to follow up later.
What the results showed
35% reduction in the risk of cancer returning in high-risk HR+ breast cancer patients after surgery.
Journal of Clinical Oncology · 2026 · NCT02326324
These findings — that in risk of cancer returning for high-risk HR+ breast cancer patients after surgery — were published in the Journal of Clinical Oncology and represent the headline result of the study.
Researchers tracked outcomes across 5,637 patients enrolled in the trial. The result was consistent enough across the group that the team felt confident reporting it.
What this means for patients
For patients with breast cancer, this result changes the calculus on what to ask their care team about. Whether it changes day-to-day care depends on factors like disease subtype, prior treatments, and where the patient is in their care journey.
What you can do now
Abemaciclib (Verzenio) is FDA-approved and available now. Eligibility depends on tumor size, grade, and lymph node involvement. Ask your oncologist whether you qualify based on your pathology report.
Eligibility for the treatments mentioned above depends on specific test results and clinical history. Bring this summary, the trial name, and your most recent labs or pathology report to your next visit.
Open breast cancer trials
A Study to Evaluate ARV-6723 Alone and With Pembrolizumab in Participants With Advanced Solid Tumors
This is a study to evaluate the safety and potential anti-tumor activity of an investigational drug called ARV-6723, in participants with advanced solid tumors. This is an open-label study which means that participants and study staff will know that all participants will receive ARV-6723. The investigational drug ARV-6723 will be given as an oral tablet on its own and also in combination with other drugs. Researchers think that ARV-6723 can help the body's immune system to better recognize, attack, and destroy cancer cells in adults with advanced solid tumors. ARV-6723 is an investigational drug, and this is the first time ARV-6723 will be used in humans. Depending on the treatment assignment, the investigational drug, ARV-6723, will be given as an oral tablet either on its own (monotherapy) or in combination with pembrolizumab, either through a vein (intravenously or IV) or through an injection beneath the skin (subcutaneously or SQ). This study will include multiple parts: In Part A1 (Phase 1a), different small groups of participants will receive lower to higher doses of ARV-6723 as monotherapy or in combination with standard-dose of pembrolizumab. In Part A2 (Phase 1b), two groups of participants with specific tumor indication(s) (TBD) will receive one of two doses selected based on information from Part A1. Details of Part B will be determined based on information generated from Part A.
ASHBY: Accelerated Super-Hypofractionated Breast Brachytherapy
The purpose of this study is to compare any good and bad effects of giving radiation treatment for breast cancer in 3 treatments over about 2 days.