Two studies reported at the recent virtual American Society of Clinical Oncology (ASCO) annual meeting showed that use of a CDK4/6 inhibitor plus fulvestrant (Faslodex) significantly improved survival for women with hormone receptor (HR)-positive, HER2-negative advanced breast cancer.
Following is a transcript of his remarks:
I think that foundationally we think of CDK4/6 inhibitors as important drugs in ER-positive disease and the data that was presented at ASCO only reaffirms that because some of the pivotal trials that we’ve heard about for the last several years were updated. The two that we’re going to talk about are PALOMA-3 and MONALEESA-3.
These were trials that looked at the comparison of fulvestrant versus fulvestrant plus a CDK. In the case of PALOMA-3, it was palbociclib. In the case of MONALEESA, it was ribociclib.
We knew these trials showed a clear improvement in PFS [progression-free survival] before and we’ve been waiting on the [overall] survival [results] from these trials. Now with longer follow-up, certainly in PALOMA-3, we see that effect. Where the effect is most pronounced are in those patients who did not receive prior chemotherapy in the advanced disease setting. But clearly with 6 years of follow-up, I think it is, in the presentation that was given at ASCO, there is a separation of the curve showing an advantage for treatment with palbociclib.
The other, I think, equally important part of that presentation was there was an effort to look at subsets of patients based on whether they had ESR1 mutations, PI3K mutations, or p53 mutations. As a generalization, if you have one of those things present, your prognosis is worse than if you don’t. But if you’re getting the CDK4/6 inhibitor palbociclib, you still get an advantage over endocrine therapy alone. Again, you make up for some of that bad prognosis that comes with those particular mutations.
In the MONALEESA-3 trial, again, we have longer follow-up. There is a survival benefit that was demonstrated that still continues now at the 5-year mark. This trial also included patients who could have received chemotherapy and it was clear that there was an advantage for those patients as well. But I think the data is consistent. It’s reassuring.