C. Kent Osborne, MD

C. Kent Osborne, MD, Founding Director of the Dan L. Duncan Comprehensive Cancer Center and the Dudley and Tina Sharp Chair for Cancer Research, Baylor College of Medicine, Houston, said in a press briefing that the results of the study were clear, but the explanation for the findings is less so.

“The results of RxPONDER clearly show no benefit to adding chemotherapy to standard endocrine therapy in postmenopausal patients, despite their having positive nodes. This emphasizes that node positivity, although an important prognostic marker, is not a predictive marker of chemotherapy sensitivity. In premenopausal patients, a different result was obtained,” Dr. Osborne said.

Most premenopausal patients received tamoxifen as their endocrine therapy. The standard approach today, however, would be ovarian suppression plus either tamoxifen or an aromatase inhibitor, both of which have proved superior to tamoxifen alone in this subgroup. Since adjuvant chemotherapy causes ovarian suppression in many premenopausal patients, the patients in the study actually underwent ovarian suppression post-tamoxifen, he pointed out, although tamoxifen alone was the endocrine therapy for the no-chemotherapy arm.

Why the Difference in Outcomes?

“Is the difference in outcomes in this subgroup due to the endocrine effects of chemotherapy? Is the benefit of chemotherapy in premenopausal patients simply a chemotherapy-induced amenorrhea and not the effect of the chemotherapy itself? Unfortunately, we may never know,” stated Dr. Osborne.

“I’m still skeptical that chemotherapy works differently in premenopausal women. I can’t imagine why that group of patients, even those with very low recurrence score, would have a different response to chemotherapy,” he continued.

“I would hate for oncologists to come away with the message that all premenopausal patients fitting these criteria should receive chemotherapy,” Dr. Osborne commented. 

DISCLOSURE: Dr. Osborne holds stock or other ownership interests in GeneTex; has served as a consultant or advisor to AstraZeneca, Genentech/Roche, Lilly, Tolmar Pharmaceuticals, and Ventana Medical Systems; holds patents or other intellectual property as Co-Editor of Diseases of the Breast; and has provided expert testimony on behalf of AstraZeneca.