Primary systemic chemotherapy in stage II-IIIb breast cancer: Independent prognostic value of molecular phenotype and the MDACC residual cancer burden—A single-institutional experience.

e21132 Background: Primary systemic chemotherapy (PSC) induces significant rates of tumor downstaging and breast-sparing surgery. However, classical histological prognostic markers are lost. The pathological Complete Response (pCR) and the residual cancer burden (RCB) score (Symmans WF, JCO.2007) have shown correlation with DFS and OS following PSC, but not in association with molecular phenotypes. Methods: Between January 1998 and April 2008, 134 consecutive patients with stage II-IIIB breast cancer were treated with PSC including anthracyclins and taxanes in our institution. 29 cases were excluded because: lack of tumor samples, lost of follow-up or prior tumor history. A new pathological evaluation for pCR, defined as absence of invasive carcinoma in the breast and regional lymph nodes, was performed. RCB was categorized as low (RCB grades 0 and I) or high (grades II and III). Phenotypic determination by IHC categorized examples as luminal A (LA), HR+/HER2-/Ki67 12%...