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Circulating Tumor DNA Following Neoadjuvant Chemotherapy and Surgery in ER-Positive and HER2-Negative Breast Cancer
Dr. Henry: So, let's look at a study entitled, “Circulating Tumor DNA Following Neoadjuvant Chemotherapy and Surgery in ER-Positive HER2-Negative Breast Cancer.” This was a subset analysis of the very large PENELOPE-B study. Circulating tumor DNA (ctDNA) is the ultimate test, I think, of where are you in the course of your cancer and how could it inform whether you're relapsing, going to relapse, what therapy should we use?
So, watch what they did. They said, "Let's take the PENELOPE-B study, which was 1 year of palbociclib, a CDK4/6 inhibitor, with endocrine therapy in breast cancer patients, hormone receptor–positive, HER2-negative, residual invasive disease after neoadjuvant chemotherapy.” The details were tricky here. What do they mean by neoadjuvant chemotherapy? So, you were eligible for the trial, probably with a large locally advanced tumor, ER-positive, HER2-negative, you got chemotherapy and then surgery. And then it was time for your endocrine therapy, hormone therapy plus CDK4/6 palbociclib. That's where this study started. They then said, "All right, before we start the hormone therapy, what's your ctDNA test?" They did it. You're on hormone therapy for 6 months, they did it again. The study went out as far as median 42 months; they did it again. And the PENELOPE-B study was 1250 patients.
Detectable ctDNA predicts relapse, indicates rethinking hormone therapy
But this subset analysis whittled down to much smaller. Overall, 78 of these patients had ctDNA analyses, which I mentioned, after pre-op chemo and surgery, then 6 months later, then as far out as 42 months. And the numbers are small, but the data were very informative. If you were positive any time along the way for that ctDNA, you were going to relapse. So, what's their take-home? And, of course, we need bigger numbers and repeat this. The take-home is, in the PENELOPE-B study, we have chemotherapy, surgery, or hormone therapy; well, if your ctDNA is positive, you're going to relapse. So, maybe you're not the appropriate person to get the hormone therapy. So, their next study will be to put those patients on a clinical trial going forward to try and do better than just hormone therapy, which may not be working at all. So again, the PENELOPE-B study presented at ASCO the subset of circulating ctDNA increasingly popular in so many of our cancers. And a lot of that was at ASCO as well.