Cancer Therapy: Clinical Cross-StratificationandDifferential RiskbyBreast Cancer Index and Recurrence Score in Women with Hormone Receptor–Positive Lymph Node– Negative Early-Stage Breast Cancer

Purpose: Previous results from the TransATAC study demonstrated that both the Breast Cancer Index (BCI) and the OncotypeDX Recurrence Score (RS) added significant prognostic information to clinicopathologic factors over a 10-year period. Here, we examined cross-stratification between BCI and RS to directly compare their prognostic accuracy at the individual patient level. Experimental Design: A total of 665 patients with hormone receptor–positive (HRþ) and lymph node–negative disease were included in this retrospective analysis. BCI andRS risk groupswere determined using predefined clinical cut-off points. Kaplan– Meier estimates of 10-year risk of distant recurrence (DR) and log-rank tests were used to examine cross-stratification between BCI and RS. Results: As previously reported, both RS and BCI were significantly prognostic in years 0 to 10. BCI provided significant additional prognostic information to theClinical Treatment Score (CTS) plus RS (DLR-c1⁄4 11.09; P < 0.001), whereas no additional prognostic information was provided by RS to CTS plus BCI (DLR-c 1⁄4 2.22; P 1⁄4 0.1). Restratification by BCI of the low and intermediate RS risk groups led to subgroups with significantly different DR rates (P < 0.001 and P 1⁄4 0.003, respectively). In contrast, restratified subgroups created by RS of BCI risk groups did not differ significantly. Conclusions: In this retrospective analysis, BCI demonstrated increased prognostic accuracy versus RS. Notably, BCI identified subsets of RS low and RS intermediate risk patients with significant and clinically relevant rates of DR. These results indicate that additional subsets of women with HRþ, lymph node–negative breast cancer identified by BCI may be suitable candidates for adjuvant chemotherapy or extended endocrine therapy. Clin Cancer Res; 22(20); 5043–8. 2016 AACR. See related commentary by Brufsky and Davidson, p. 4963