CDK4/6 Inhibitors in HR+ Advanced Breast Cancer - Episode 2
Debu Tripathy, MD: In terms of the comparisons and differences between palbociclib and ribociclib, the results are very comparable.
The top line results in first-line, compared to aromatase inhibitors, are very, very similar if you look at PALOMA-2 and MONALEESA-2 in terms of the overall hazard ratio of around 0.5, doubling of time to disease progression. There was an interesting update from the MONALEESA-2 looking at survival that seemed to show maybe a very early trend. It was close to achieving statistical significance, and that’s the first survival signal we’ve seen. We’ll have to follow these trials out longer and see if that does emerge. Health-related quality of life is preserved in both groups. That’s always one concern whether the toxicities might outweigh in some way and show up in quality of life, but that didn’t turn out to be the case. So, we’re getting this doubling of disease-free survival without a compromise in that.
The safety profile is very similar, neutropenia being the most common, but rarely does that result in febrile neutropenia. The febrile neutropenia rates are about the same. The number of people who have to discontinue due to side effects is about the same. There’s maybe a touch more in terms of transaminase elevations with ribociclib, so the monitoring is a little bit different. The prolongation of the QTc interval was seen more prominently, but many drugs in this class, and of course many drugs in general, cause that prolongation. It does mean EKG monitoring, but in terms of the number of patients who may suffer significant side effects from this, again, very comparable.
So, one of the things that we tend not to think about as much, but is critically important to our patients and is a logistical issue, is how the drug is actually delivered to the patient and what the patient sees. And there are 2 aspects that are different between palbociclib and ribociclib. One is that the dosing of ribociclib is in multiples of the pills. When you dose-reduce from 600 mg to 400 mg, it’s just a matter of taking one less pill or from 400 mg or to 200 mg. And that’s the dosing reduction scheme that was used in the trials. And then having it co-packaged with letrozole also facilitates the drug delivery, the hassles that a patient has to go through to get any drug, that’s an interesting feature as well.
Transcript Edited for Clarity