Molecular subgroup of high-grade serous ovarian cancer (HGSOC) as a predictor of outcome following bevacizumab.

5502 Background: HGSOC is a histopathological diagnosis and may represent multiple diseases at a molecular level. We investigated whether distinct molecular subgroups may influence treatment choice. Methods: mRNA was extracted from 265 macrodissected formalin fixed paraffin embedded HGSOCs from Scottish patients (pts) treated with primary debulking then platinum based chemotherapy. Transcriptional analysis was performed using the Ovarian DSA microarray. This was repeated using 283 UK samples from the ICON7 study [first line paclitaxel/carboplatin +/- concomitant and maintenance bevacizumab (bev) for 12 months]. Results: Unsupervised hierarchical clustering (Scottish tumours) identified three major subgroups, two with angiogenic gene upregulation and one with angiogenic gene repression and immune gene upregulation. This latter ‘immune’ subgroup had a superior overall survival (OS) compared to the other two subgroups combined [HR = 0.66 (0.46-0.94)]. A 63-gene expression signature to prospectively identify ...