Debra Patt, MD, MPH, MBA

Those of us who see and treat patients with breast cancer know the advent of CDK 4/6 inhibitors for the treatment of patients with ER-positive metastatic breast cancer has been remarkable. We have so many patients who take endocrine therapy and a CDK 4/6 inhibitor and — for many years — we have been able to talk about the benefit in PFS, which is nearly triple for patients who receive this unique therapy.

In the MONALEESA-7 trial — in which researchers studied ribociclib in combination with endocrine therapy for patients with advanced breast cancer — we not only saw a PFS benefit, as expected, but also an OS benefit. This confirms what we have suspected for a long time.

In the space of CDK 4/6 inhibition we have three drugs — palbociclib (Ibrance, Pfizer), ribociclib and abemaciclib (Verzenio, Eli Lilly). They are different medications with different costs, dosing schedules and toxicities. But, they continue to be clinically meaningful in making advanced breast cancer a chronic disease for many of our patients.

Harold J. Burstein, MD, PhD, FASCO

The theme we are seeing in this presentation is that, with mature and robust data, we are now achieving substantial improvements in survival with the innovative drugs that are coming to our market. This is an important study because it shows that this widely used class of drugs, CDK 4/6 inhibitors, will delay the time to the need for chemotherapy for advanced breast cancer, and will really double the effectiveness of endocrine therapy. This now also translates into a significant survival benefit for women who have ER-positive metastatic breast cancer.

It’s also significant because, as Dr. Hurvitz mentioned, this study focuses on a group of young women. Many people think of young women as having different types of breast cancer, like triple-negative breast cancer or HER2-positive breast cancer. In fact, the most common form of breast cancer in young women is ER-positive breast cancer. This is the largest study in recent memory that is focused exclusively on premenopausal women, and shows that they, too, benefit from this class of drugs in a remarkable way.

Finally, in an era when we are thinking about value in oncology care, the demonstration of a robust survival difference substantially adds to a value proposition for products like ribociclib. So hopefully, these data will enable access to this product to more women around the world, particularly in health care systems that assess value rigorously as part of their decisions for national access to drugs.

Overall, these are important survival data in a group of patients historically understudied, showing a clear benefit and establishing value of this class of drugs in the management of the most common form of breast cancer.

Kevin Kalinsky, MD

These data are exciting because, when adding targeted therapy to endocrine therapy, we are observing a survival benefit. We had known that there was an improvement in PFS but now we see, in the frontline setting with the CDK 4/6 inhibitor, improvement in survival.

This is the only premenopausal-only study. To have achieved an OS benefit is quite remarkable in these frontline patients.

This study will certainly change the consideration of CDK 4/6 inhibitors in frontline patients with premenopausal disease. Because we’d seen an improvement in PFS, our practice pattern has been to give hormonal therapy with the CDK 4/6 inhibitor upfront. However, there are other clinicians who would perhaps argue that we should wait to see if a survival benefit will be achieved. These data could convince these providers who haven’t been using it as frontline treatment that there is a survival benefit. That could be further compelling evidence that they might have been waiting for.

The other remarkable finding of this study is the response rate. This is further evidence of how CDK 4/6 inhibitors have been paradigm-shifting. We used to think that we needed to start with chemotherapy in these patients, but this study shows quite remarkable responses with the combination of hormonal therapy and CDK 4/6 inhibitors. The kind of responses we’ve seen in this study will hopefully further compel treating physicians to use this combination.

Kristen D. Whitaker, MD

To see improved OS with the addition of a CDK 4/6 inhibitor to endocrine therapy, especially in premenopausal women who often have aggressive disease, is really exciting for our patients.

Improving OS with cancer therapies is the ultimate goal, but often hard to achieve. It’s excellent that we now have a CDK 4/6 inhibitor in our arsenal that hits the improved OS mark. It also may be helpful in the selection of the best CDK 4/6 inhibitor for premenopausal women.