Recapping the RxPONDER Trial at the 2020 San Antonio Breast Cancer Symposium

Announcer:
Welcome to Breaking Boundaries in Breast Cancer on ReachMD, sponsored by Lilly. On this program, we’ll hear from Dr. Lajos Pusztai, Professor of Medicine and Director of Breast Cancer Translational Research at Yale Cancer Center and Yale School of Medicine. Dr. Pusztai is here to share some advancements in early breast cancer that were featured at the 2020 San Antonio Breast Cancer Symposium. Let’s hear from him now.

Dr. Pusztai:
So I’m delighted to draw your attention to one of the most important trials that I think was presented this year at the San Antonio Breast Cancer Symposium. And this is a study that is the SWOG 1007 or RxPONDER trial that was released by the SWOG Breast Committee. These are the first results of the study. The study started about 13 years ago and asked a really important clinical question: whether women who are ER-positive and has one to three positive lymph nodes, and also have a low recurrence score, defined as 0 to 25, would benefit from regimen chemotherapy in addition to endocrine therapy, or endocrine therapy is sufficient alone. The study randomized 5,000 patients and included patients from five different countries.

And the results were somewhat surprising. Overall, there was a very small benefit from chemotherapy, but that small benefit was actually restricted to the premenopausal population. And the benefit in the premenopausal population was quite substantial. On the other hand, the larger segment of the population in the trial, the postmenopausal women, who included about 3,200 patients, did not derive any benefit whatsoever from chemotherapy, regardless of the actual recurrence score within that range of 0 to 25.

The study also asked the statistical question, whether the recurrence score value predicts chemotherapy benefit. The value, within 0 to 25, did not predict benefit, but the menopausal status did. So the premenopausal women derived an absolute 5% improvement in invasive recurrence-free survival if they received chemotherapy. The 5-year invasive recurrence-free survival went from 89% in the control group to 94% in the chemotherapy group. And this translated into an approximately 50% relative improvement in reducing metastatic recurrences.

This is a really important finding because it really sort of answers the question that we all struggle within the clinic, of how to manage patients with one to three positive nodes and a low recurrence score. That’s a fairly sizable population in the United States due to the mammographic screening prevalence and the prevalence of treatment because of the broad use of the recurrence score. So I’m very happy to share with you the results that we now have the answer. So the postmenopausal women do not benefit from chemotherapy, even if they have positive nodes. The premenopausal women do.

The trial did not answer all the questions that we would like to know the answer to. For example, they can’t really answer the question from the context of this trial, to what extent the cytotoxic effect of the chemotherapy drives the benefit versus its effect on inducing ovarian suppression and premature ovarian failure in women who are still premenopausal in their age, between 40 to 50. So that’s an important question to answer in the next sort of generation of trials.

Announcer:
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