258PD - Investigating the Clinical Relevance of Genomic Characteristics in Luminal a and B Breast Cancer (Bc)

Abstract

ABSTRACT Aim: To address the major challenge of understanding the clinical relevance of the increasingly available large amount of tumour genomic data in BC. Methods: Histologically reviewed, paraffin tumour DNA samples (N = 1092) from patients who had received anthracycline-based adjuvant chemotherapy in the frame of two randomized trials by HeCOG (HE10/00, pre-trastuzumab; HE10/05, post-trastuzumab era), were investigated with targeted massively parallel sequencing (Ion Torrent systems) for variants in 58 genes implicated in BC. Upon multiple stringent quality filters, pathogenic mutations (mut) and allelic imbalance (AI) were evaluable in 844 cases (77.3%). IHC4 was used for BC subtyping. Results: Mut were observed in 499 and AI in 497 tumors (59%), reaching up to 55 and 20 affected genes in single tumours, respectively. Mut and AI often coexisted (p Conclusions: Combined assessment of AI and mutation status may provide useful prognostic information in patients with luminal A and B tumours treated with adjuvant anthracycline-based chemotherapy. Disclosure: R. Wirtz: Dr R.W. has pending patent applications; G. Fountzilas: On behalf of the Hellenic Foundation for Cancer Research, Prof. G.F. has pending patent applications. All other authors have declared no conflicts of interest.