More about endocrine therapy in RxPONDER
Dr. Osborne said that premenopausal women in RxPONDER were “nearly always” prescribed tamoxifen.
However, he observed that the current standard approach to treatment in this age group would be ovarian suppression plus either an aromatase inhibitor or tamoxifen, “both of which have been shown to be superior to tamoxifen alone in this subgroup.
“Since the adjuvant chemotherapy causes ovarian suppression in many premenopausal patients,” he said, “these patients then, in fact, received ovarian suppression plus tamoxifen,” rather than tamoxifen alone for the group that did not receive chemotherapy.
Dr. Osborne asked a question that came up again and again during the postpresentation discussion: “Is the difference in outcome in this subset due to the endocrine effects of chemotherapy? Unfortunately, we may never know the answer to this question,” he said.
Dr. Kalinsky replied that whether the difference in benefit of chemotherapy in premenopausal women “was a direct benefit, meaning that there’s something about the biology difference” between tumors in premenopausal versus postmenopausal women, “or whether this was an indirect effect, meaning impacting rates of amenorrhea... is not specifically how this study was designed.”
However, an exploratory landmark analysis at 6 months suggested that the use of ovarian suppression with endocrine therapy did not have an effect on outcomes.
Dr. Osborne said he is nevertheless “still skeptical that chemotherapy works differently in premenopausal women. Until we show that it’s not an endocrine effect ... I just can’t imagine why that group of patients, even the ones with very low Oncotype [score], would have a different response to chemotherapy.”
He added: “If I can think of a rationale ... I would believe it, but right now, I’m a little bit skeptical.”
Virginia Kaklamani, MD, of the University of Texas Health San Antonio Cancer Center, San Antonio, who is a meeting codirector, said she wanted to “second that.
“I honestly think that this is an OFS [ovarian function suppression effect] that we are seeing. We have several clinical trials that have been done looking at ovarian function suppression versus not ... showing that [it] can help as much as chemotherapy.”
Dr. Kaklamani continued: “Unfortunately, the arms to those trials were not perfect for now, and this is going to be an unanswered question until we have a large trial comparing OFS to chemotherapy.”
The study was sponsored by the National Cancer Institute, the Susan G. Komen for the Cure Research Program, the Hope Foundation for Cancer Research, the Breast Cancer Research Foundation, and Exact Sciences. Dr. Kalinsky, Dr. Osborne, and Dr. Kaklamani report financial ties to multiple pharmaceutical companies.
This article first appeared on Medscape.com.