Prediction of 10-Year Chemotherapy Benefit and Breast Cancer-Specific Survival by the 21-Gene Recurrence Score (RS) Assay in Node-Positive, ER-Positive Breast Cancer – An Update of SWOG-8814 (INT0100).

Background: A low 21-gene RS identifies patients with ER-positive breast cancer who do not appear to benefit from anthracycline-based chemotherapy (CAF) added to tamoxifen (T) despite positive axillary lymph nodes (Albain KS, et al. Lancet Oncology, In Press). However, in the low RS group, the lack of improvement by CAF in the 64% disease-free survival (DFS) at 10 years is not considered definitive evidence against the use of chemotherapy for conventionally-identified high risk patients. We conducted new DFS prediction analyses within nodal categories by RS over 10 years and assessed whether the assay has predictive utility for breast cancer specific survival (BCSS).Methods: RT-PCR analyses for the 21 gene RS assay were feasible in 148 patients on T from the parent trial treated and 219 on CAF followed by T, as previously described. In this update, we conducted 10-year DFS analyses within nodal categories 1-3+ and 4+ by the linear RS. For the exploratory analysis of BCSS, only deaths due to breast cancer were counted as events, censoring deaths due to other causes (such as late cardiovascular events) as well as patients alive at the last follow-up visit. The clinically-utilized (trichotomized) RS categories of low ( Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 112. NOTE: This abstract was accepted for presentation at the Symposium after the Abstract Book went to press.