Results of RxPONDER in HR+ Breast Cancer

Dr Andrew Seidman reacts to outcomes of the RxPONDER trial of chemotherapy use in women with HR-positive breast cancer at low risk of recurrence.

Sara Hurvitz, MD: Andrew, let’s move now into probably the biggest news at the San Antonio Breast Cancer Symposium. I was involved in a panel, and we all had to go around and say what we thought was the biggest data at San Antonio—and this was unanimously selected, except by the main author, who is too humble to name it. Let’s talk about the RxPONDER trial. These data in lymph node-positive breast cancer have been long awaited, and the results were a little confusing. Again, this is 1 of the slide decks that I had to go through 2 or 3 times to really digest. Can you talk to me about this trial, its end points, how it differed from TAILORx, and what your conclusions were after seeing the data presented?

Andrew Seidman, MD: Yes, I’m not sure I found it as confusing as some, and I want to compliment Kevin Kalinsky MD, MS, a former Fellow from MSK [Memorial Sloan Kettering Cancer Center], who I couldn’t be more proud of for doing such a great job in communicating it. This was a much awaited study that probably will have the biggest practice impact change, where both pre and perimenopausal women with 1 to 3 positive nodes, about 5000 or so were randomized to endocrine therapy alone or endocrine plus chemotherapy. These women, importantly, they had to be considered to be able to get anthracycline and taxane therapy, so you are selecting out patients who passed that litmus test, and patients with recurrence scores from 0 to 25 were those randomized.

The overall result for the entire intent-to-treat population did not show the benefit for chemotherapy, but the preplanned subset analysis for premenopausal women did show a benefit in those patients. When you parse that further, based on subgroups of recurrence score 0 to 13, or 14 to 25, you see what you would expect, the signal for greater benefit the higher the recurrence score for chemotherapy. But even for premenopausal women in the recurrence score of 0 to 13 category, there was about a 4% benefit in invasive disease-free survival and about 6% for those with recurrence scores of 14 to 25.

The big high-level message here is that this is good news for a lot of postmenopausal women with N1 disease who now can safely forego chemotherapy. That’s a big sea change. One can always find subsets where you may have greater concern. The number of patients with, for example, 3 positive nodes was not huge. We don’t have information yet about the potential meaning of extracapsular extension, when you have those nodes that are significantly involved. Overall, again, from a very high level, this is an important trial that leads to meaningful de-escalation for a lot of patients.

Transcript edited for clarity.

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