Dr. Kaklamani on Racial Disparities and Clinical Outcomes in the RxPONDER Trial in Breast Cancer

Virginia Kaklamani, MD, professor of medicine, leader, Breast Cancer Program, UT Health San Antonio, MD Anderson Cancer Center, discusses how racial disparities may affect patient outcomes and treatment expectations based on data from the RxPONDER (NCT01272037) trial in breast cancer.

The RxPONDER trial demonstrated that the 21-gene recurrence score has clinical utility in randomizing women with estrogen receptor (ER)–positive, lymph node–positive breast cancer to receive or not receive chemotherapy. Notably, patients included in this trial exhibited at least 1 to 3 positive lymph nodes. Overall findings from RxPONDER indicated that premenopausal women appeared to benefit more from adjuvant chemotherapy vs postmenopausal women.

A subsequent analysis was performed to investigate the existence of racial and ethnic disparities among patients enrolled in the trial and determine their effect on patient outcomes.

The analysis, presented at the 2022 San Antonio Breast Cancer Symposium, showed that non-Hispanic, Black patients with hormone receptor (HR)–positive, HER2-negative breast cancer were more likely to experience poorer outcomes compared with non-Hispanic White, Asian, and Hispanic patients. This patient subgroup displayed worsened distant relapse-free survival and 5-year invasive disease-free survival rates. Additionally, patients across racial and ethnic groups were randomized to treatment in the same fashion and had similar 21-gene recurrence scores.

Initial explanation for these findings proposed that Black patients may be less compliant to endocrine therapy. However, data showed that this patient population demonstrated increased compliance compared with non-Hispanic White patient’s in regard to both general treatment assignments and treatment with endocrine therapy. Accordingly, assignment to a given treatment arm did not affect patient outcomes.

Adjustment for other clinical and pathologic characteristics including recurrence score, age, and grade also did not alter or explain this result.

This suggests that a lack of treatment compliance cannot explain the disparity in long-term outcomes between Black and non-Hispanic, White women. Instead, a biologic difference in HR-positive breast cancer in Black women may be associated with increased risk.

Editor's note: Dr. Kaklamani reports serving as a consultant or on a paid advisory board for Puma, AstraZeneca, Athenex and Gilead; she is on the speaker’s bureau for Pfizer, Gilead, Genentech, Genomic Health, Puma, Eisai, Novartis, AstraZeneca, Daiichi Sankyo and Seagen and Research with Eisai.