Terry L. Evans, MD
CDK4/6 inhibitors have been game-changing treatments for patients with hormone receptor (HR)–positive metastatic breast cancer, said Terry L. Evans, MD.
State of the Science Summit™ on Breast Cancer, Evans, a medical oncologist and clinical assistant professor of medicine at the University of Pittsburgh Medical Center, discussed the impact of CDK4/6 inhibitors in the metastatic breast cancer space and challenges that still need to be addressed.
OncLive: Is there an optimal partner for each of these CDK4/6 inhibitors?
: I don’t think it matters. All of the trials used letrozole or anastrozole [as partner drugs]; I don’t think there’s any difference. In MONALEESA-7, the premenopausal study, everybody had to receive goserelin monthly and then investigators paired it either with tamoxifen, letrozole, or anastrozole, and it seemed to make no difference what the partner drug was.
These drugs in partnership with tamoxifen or an AI are useful in patients who are pre-, peri-, and postmenopausal, so I wouldn’t hesitate to use them in any subgroup.
Could you discuss the impact of trials such as PALOMA-3 on the space?
The PALOMA-3, MONALEESA-3, and MONARCH 2 trials all paired a different CDK4/6 inhibitor with the same secondline therapy, which was fulvestrant. All the data are the same; I don’t think there’s a bit of difference in terms of efficacy among palbociclib, ribociclib, and abemaciclib. The cost is the same as well. In practice, [physicians] have to decide which group of patients they feel the most comfortable giving [each inhibitor to] because of toxicity.
Is toxicity an issue with this class of agents?
The tolerability is a big issue. My own sense is that abemaciclib may be a more potent drug when it comes to inhibiting breast cancer metastases. In MONARCH 3, when abemaciclib was combined with fulvestrant, there were tumor shrinkages in 14 of the patients. You hardly ever see tumor shrinkage with cytostatic drugs, and so, it may be a better drug. We need to get more data on that particular issue, but from the standpoint of adverse events, that is where clinical judgment comes into play.
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