medwireNews: Menopausal status could help treatment decision-making for early hormone receptor (HR)-positive, HER2-negative breast cancer (BC) with a low risk of recurrence, say the SWOG S1007 RxPONDER investigators who believe premenopausal, but not postmenopausal, patients benefit from chemotherapy before endocrine therapy.
Reporting the findings at the 2020 San Antonio Breast Cancer Symposium, Kevin Kalinsky (Winship Cancer Institute of Emory University, Atlanta, Georgia, USA) explained that the study recruited patients who had between one and three positive lymph nodes and a genome-based Oncotype Dx recurrence score (RS) of up to 25 out of a possible 100.
Kevin Kalinsky discusses the SWOG S1007 RxPONDER trial
The 2509 participants who received anthracycline- or taxane-based chemotherapy before endocrine therapy had significantly better invasive disease-free survival (IDFS) than their 2506 counterparts who received only endocrine therapy (92.4 vs 91.0%, hazard ratio [HR]=0.81).
Although the primary analysis did not find evidence of a significant relationship between a lower RS score and a reduced benefit from chemotherapy, there was a significant interaction between receipt of chemotherapy and menopausal status.
Among the 1655 premenopausal patients, women given chemoendocrine therapy had a significantly better 5-year IDFS rate than those who received only endocrine therapy (94.2 vs 89.0%, HR=0.54), whereas a treatment effect was not found among the 3350 postmenopausal patients (91.6 vs 91.9%).
And forest plot analysis suggested an IDFS benefit from the addition of chemotherapy occurred across patient subgroups of age, tumor grade and size, positive lymph nodes and RS only for the premenopausal patients, although the presenter commented that some of these groups were small and therefore had wide confidence intervals.
A 5-year overall survival benefit with chemoendocrine therapy versus endocrine therapy was also identified for the premenopausal patients (98.6 vs 97.3%, HR=0.47), but not their postmenopausal counterparts (96.2 vs 96.1%).
Of note, premenopausal women who received chemoendocrine therapy were less likely to have distant recurrence as a first event than those given only endocrine therapy (3.1 vs 6.0%), but no difference was detected between the treatment arms in the postmenopausal cohort (2.3 vs 2.6%).
Kevin Kalinsky summarized the findings as indicating “postmenopausal women with positive nodes and recurrence score 0–25 can likely safely forgo adjuvant chemotherapy without compromising IDFS” whereas “premenopausal women with positive nodes and RS 0–25 likely benefit significantly from chemotherapy.”
He concluded that “additional follow-up is ongoing, and future analyses will also include [quality of life] and other outcomes.”
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