Endocrine Therapy Alone Is Not Inferior to Chemoendocrine Therapy in Breast Cancer With Oncotype DX Scores Between 11 and 26

CHICAGO—Adjuvant endocrine therapy (ET) alone may not be inferior to chemotherapy plus endocrine therapy (CET) among women with hormone-receptor (HR) positive, HER2-negative, axillary node (AN)-negative breast cancer and Oncotype DX Recurrence Score (RS) between 11 and 25, according to findings presented in the Plenary Session at the American Society of Clinical Oncology 2018 Annual Meeting on Sunday, June 3.¹

Previous studies have shown that a low RS score of less than or equal to 10 among women with HR-positive, HER2-negative, AN-negative breast cancer is prognostic for low recurrence with ET, and a score of 26 or more is predictive of deriving benefit from chemotherapy. The effect of combination chemotherapy and ET, however, has not been fully clarified among patients with RS scores between 11 and 25.

For the prospective, phase 3 TAILORx study (ClinicalTrials.gov Identifier: NCT00310180), researchers randomly assigned 10,253 women with breast cancer between the ages of 18 and 75 who agreed to have their treatment according to their RS score: patients with RS 10 or less were assigned to ET, patients with RS between 11 and 25 were randomly assigned to receive ET or CET, and patients with RS 26 or higher received CET.

Of the study participants, 65.5% (6711) had an RS of 11 to 25 and adequate data for analysis. The median follow-up was 90 months.

Results showed that among patients with RS score 11 to 25, invasive disease-free survival (iDFS) for ET was non-inferior compared with CET (hazard ratio [HR], 1.08; 95% CI, 0.94-1.24; P = .26). Further evaluation also revealed that the distant recurrence-free interval (DRFI; HR 1.03; P = .80), recurrence-free interval (RFI; HR 1.12; P = .28), and overall survival (OS; HR 0.97; P = .80), were also non-inferior with ET when compared with CET.

The long-term rates of iDFS, DRFI, RFI, and OS, were nearly identical between patients receiving ET and CET after 9 years.

Nearly 42% (338) of first iDFS events were cases of recurrence; 23.8% (199) of cases were distant recurrences.

Treatment interactions tests showed that age significantly affected iDFS and RFI, but grade, tumor size, menopause, and RS score (continuous or RS 11-15, 16-20, 21-25) did not.

Read more of Cancer Therapy Advisor‘s coverage of the American Society of Clinical Oncology (ASCO) 2018 meeting by visiting the conference page.

Reference

1. Sparano JA, Gray RJ, Wood WC, et al. TAILORx: Phase III trial of chemoendocrine therapy versus endocrine therapy alone in hormone receptor-positive, HER2-negative, node-negative breast cancer and an intermediate prognosis 21-gene recurrence score. Oral presentation at: 2018 ASCO Annual Meeting; June 1-5, 2018; Chicago, IL.