Development and Validation of the RSClinN+ Tool to Predict Prognosis and Chemotherapy Benefit for Hormone Receptor–Positive, Node-Positive Breast Cancer

PURPOSE Clinicopathological factors and the 21-gene Oncotype DX Breast Recurrence Score (RS) test both influence prognosis. Our goal was to develop a new tool, RSClinN+, to individualize recurrence risk and chemotherapy benefit predictions by menopausal status for patients with HR+/human epidermal growth factor receptor 2–negative, lymph node–positive breast cancer by integrating the RS result with clinicopathological factors (grade, tumor size, age). METHODS We used patient-level data from 5,283 patients treated with chemoendocrine therapy (CET) versus endocrine therapy alone (ET) in the S1007 (N = 4,916) and S8814 (N = 367) trials to develop the tool. Cox proportional hazards regression models stratified by trial were used to estimate 5-year invasive disease-free survival for pre- and postmenopausal woman, respectively. The integrated RSClinN+ model was compared with RS alone and clinicopathological models using likelihood ratio tests. Absolute CET benefit was estimated as the difference between ET and CET risk estimates. Validation of RSClinN+ was performed in 592 patients with node-positive disease in the Clalit Health Services registry. RESULTS RSClinN+ provides better prognostic information than RS model alone (premenopausal P = .034; postmenopausal P < .001) or clinicopathological model alone (premenopausal P = .002; postmenopausal, P < .001). In postmenopausal women, RS showed interaction with CET benefit ( P = .016), with RSClinN+ absolute CET benefit ranging from <0.1% to 21.5% over RS ranges 0-50. In premenopausal patients with RS ≤25, there was no significant interaction between RS and CET benefit. In external validation, RSClinN+ risk estimates were prognostic (hazard ratio, 1.75 [95% CI, 1.38 to 2.20]) and concordant with observed risk (Lin's concordance, 0.92). CONCLUSION RSClinN+ provides improved estimates of prognosis and absolute CET benefit for individual patients compared with RS or with clinical data alone and could be used in patient counseling.