A RB-1 loss of function gene-signature (RBsig) as a tool to predict response to neoadjuvant chemotherapy (CT) plus anti-HER2 agents (H): A substudy of the NeoALTTO trial (BIG 1-06).

570 Background: CT added to H is the treatment of choice in HER2+ early breast cancer (BC) patients (pts). However HER2+ tumors are clinically and biologically heterogeneous and treatment response varies significantly by hormone receptor (HR) status and molecular subtype. Predictive biomarkers are needed in this context. We have previously shown that RBsig expression correlates with pathological complete response (pCR) rate following CT +/− H in...