Matthew Goetz, MD, Mayo Clinic, Rochester, MN, discusses a second interim analysis on overall survival (OS) results for the MONARCH 3 trial, demonstrating prolonged OS with the addition of abemaciclib to a nonsteroidal aromatase inhibitor (NSAI) for patients with HR-positive, HER2-negative advanced breast cancer. However, these results did not meet the threshold for formal statistical significance.

Dr Goetz presented these findings at the 2022 European Society for Medical Oncology (ESMO) Congress.

Transcript:

Hi, my name is Dr. Matthew Goetz. I'm a Medical Oncologist at the Mayo Clinic in Rochester, Minnesota. The MONARCH-3 clinical trial was a study that was testing whether the addition of a CDK4/6 inhibitor improved progression-free survival when added to standard-of-care hormonal therapy, in this case a nonsteroidal aromatase inhibitor.

There are 3 trials, testing 3 different CDK4/6 inhibitors in the first-line setting. Palbociclib in PALOMA-2, ribociclib in MONALISA-2, and abemaciclib in MONARCH-3. All 3 trials have demonstrated that the addition of these CDK4/6 inhibitors to standard-of-care hormonal therapy improve progression-free survival, and that's led to regulatory approval.

In the last year or so, we've begun to see some of the survival data come out from these trials. We've seen a survival advantage for the addition of ribociclib to hormonal therapy, but we didn't see that benefit with palbociclib in the PALOMA-2 data that we just presented at the American Society of Clinical Oncology Annual Meeting. I think clinicians have been anticipating the results of MONARCH-3 —would it be like PALOMA-2 or would it be more like the MONALISA data? We presented here at this conference, the second planned interim analysis for overall survival, and what we found was that in the intent-to-treat population, the addition of abemaciclib to a non-steroidal [aromatase inhibitor] AI improved overall survival by a little more than 12 months.

Additionally, we also had a preplanned analysis in patients that had visceral disease, and this is a group of patients that have higher risk characteristics, generally poor prognosis, and here the addition of abemaciclib to standard-of-care hormonal therapy improved its overall survival by 16 months.

It's important to note that in both of these groups there was a stopping boundary that was set up to determine whether we would actually stop the trial or not. And although the p-value was less than 0.05 for both of these analyses, the stopping boundary was not crossed, and therefore, we will continue to follow these patients for the final overall survival results which we anticipate in 2023.

Source:

Goetz M, Toi M, Huober J, et al. MONARCH 3: Interim overall survival (OS) results of abemaciclib plus a nonsteroidal aromatase inhibitor (NSAI) in patients (pts) with HR+, HER2- advanced breast cancer (ABC). Presented at: ESMO Congress; September 9-13, 2022. Paris, France and virtual. Abstract LBA15.