Assisting Community-Based Oncologists and Surgeons in Making Neoadjuvant Treatment Decisions for Patients with Early Breast CancerResponse to chemotherapy/anti-HER2 treatment based on ER status
2:16 minutes.
TRANSCRIPTION:
DR BLACKWELL: We know that there’s a difference in a complete pathologic response for a patient who’s facing ER-positive — potential pathologic response in a patient facing ER-positive, HER2-positive versus ER-negative, HER2-positive. And I don’t think anyone really knows the biology. I could come up with some very extensive, elegant reasons why this might be. It has to do with proliferation, synergy between antiproliferative effects and immune effects induced by trastuzumab. But I don’t know if we really know, but one thing that is consistent is that there is a lower likelihood of a complete pathologic response in this ER-positive subgroup. And I think it probably is going to be primarily related to the proliferation of the inherent tumor being treated. DR MAMOUNAS: But the interesting observation was very intriguing, is that in the adjuvant trials, the benefit from trastuzumab is equally seen in ER-positive and ER-negative patients when it comes to reducing distant recurrence. So apparently micrometastases are equally sensitive to anti-HER therapy, but maybe the primary tumor doesn’t have enough time to go through pathologic complete response, but certainly the micrometastases must be affected. So going back to proliferation. It’s possible that maybe if you gave therapy for a longer period of time in the ER-positive patients, you may have elicited more pathologic responses in the future, but we don’t know that. DR LOVE: I mean, kind of it reminds us of the paradigm we’re facing in HER2-negative disease, where we think about ER-positive not being as proliferative and maybe not responding as much to chemo? DR MAMOUNAS: Right. Yes. But the other issue may be also that if you look at the pure HER2 subtype based on microarray data, usually those are the hormone receptor-negative, HER2-positive. Some of the ER-positive, HER2-positive are the luminal B, or luminal HER2 subtype, as we call them. So they may not be as sensitive. Now the data there are somewhat debatable, because some studies have shown that indeed pathologic complete response is much higher in the HER2 subtype versus the non-HER2 subtype. Our data from the neoadjuvant B-41 trial did not support this. We saw similar pathologic responses in the HER2 subtype, defined by microarray data, versus the non-HER2 subtype. |