Adding ribociclib (Kisqali) to endocrine therapy led to a significant improvement in invasive disease-free survival for people with hormone receptor (HR)-positive, HER2-negative early-stage breast cancer, according to the phase III NATALEE trial, which was presented by , of the University of California Los Angeles, at the American Society of Clinical Oncology (ASCO) annual meeting.
In this exclusive ľֱ video, Slamon discussed the findings from the study.
Following is a transcript of his remarks:
The NATALEE study was designed to test one of the three approved CDK4/6 inhibitors that are approved for advanced breast cancer in the early breast cancer setting.
So the three drugs are palbociclib [Ibrance], ribociclib, and abemaciclib [Trodelvy]. Palbociclib was the first out of the gate to be approved for advanced disease. It was tested in early disease and those randomized trials showed that it did not meet any kind of meaningful endpoint. So it's not been approved for early disease. Abemaciclib has been approved, but it really focused on the highest-risk patients in early breast cancer.
The NATALEE trial looked at a broader population of breast cancer patients, stage II and stage III. So those that would be considered at intermediate risk, not just the highest risk, including node-negative patients, which normally aren't considered at high risk unless they have other features. For all those reasons, it was a broader trial and a broader population.
And in the end, it's shown that it will overall decrease the recurrence rate by 25% and decrease the incidence of metastatic disease by 26%. So it met its primary endpoint of decreasing invasive disease-free survival at its second efficacy analysis. So there's still ongoing follow-up, but it already passed what's called the O'Brien-Fleming boundary, where the safety monitoring committee declares the trial finished. So you don't continue to accrue patients on a control arm if you have something that might be better.
I think physicians will still want to see maturation of the data. And one of the exciting things about the NATALEE trial is we saw this difference at a very early point in the trial. Meaning only 20% of the patients have made it to the third year of their treatment. They're supposed to receive 3 years of treatment with the drug. We know they're past the period where they'll have any safety problems. So we have another 80% of the patients on treatment. They're going to get out the 3 years.
I think that's hopeful that things might improve even further. So there are going to be further follow-ups. They're planned in the protocol and that's going to happen.
I think the main thing for the treating physician, it gives a bigger population of patients that can benefit. And decreasing the recurrence rate by as much as 25% on a relative basis, or 3.3% on an absolute basis, I think is a meaningful impact on patients with this disease.
We know that patients with early breast cancer, with stage II disease, a third will have a recurrence, can be as far out as 2 or 3 decades. Patients with stage III disease, even though it's early breast cancer, can have recurrences of more than 50% out in 2 or 3 decades. So I think this is all positive data.