Agreement in Risk Prediction Between the 21-Gene Recurrence Score Assay (Oncotype DX®) and the PAM50 Breast Cancer Intrinsic Classifier™ in Early-Stage Estrogen Receptor–Positive Breast Cancer

Purpose. To compare risk assignment by PAM50 Breast Cancer Intrinsic Classifier™ and Oncotype DX_Recurrence Score (RS) in the same population. Methods.RNAwasextractedfrom151estrogenreceptor (ER) stage I–II breast cancers and gene expression profiled using PAM50 “intrinsic” subtyping test. Results. One hundred eight cases had complete molecular information; 103 (95%) were classified as luminal A (n 76) or luminal B (n 27). Ninety-two percent (n 98) had a low (n 59) or intermediate (n 39) RS. Among luminal A cancers, 70% had low (n 53) and the remainder (n 23) had an intermediate RS. Among luminal B cancers, nine were high (33%) and 13 were intermediate (48%) by the RS. Almost all cancers with a