Use of molecular classification combined with p53 and topoisomerase IIa expression to identify tumors highly responsive to FEC regimen: A tissue microarray

546 Background: Identification of highly responsive tumors to specific regimen is needed in order to better tailor post-operative chemotherapy regimen. We previously reported using a tissue microarrays that basal-like and HER2-overexpressing tumors derive higher benefit from adjuvant chemotherapy than luminal-like tumors. Previous studies have reported that p53+/basal-like tumors, and HER2+/topoisomerase IIa + tumors were highly sensitive to alkylating agents and anthracyclines respectively. In the present study, we have evaluated whether p53+/basal-like and HER2+TopIIa+ tumors derive high benefit from an alkylating/anthracyclines based chemotherapy. Methods: A tissue microarrays was built with tumor samples from 823 patients randomized between FEC/FAC regimen and no chemotherapy. Basal-like breast cancers were defined as HER2-/ER-/EGFR+ and/or CK5/6+ tumors. HER2-overexpressing were defined using HER2 expression by IHC (3+ score). P53 and topoisomerase IIa expression were assessed by IHC. Treatment effec...