Oxford Classic-defined EMT risk stratification of High Grade Serous Ovarian cancer for guiding treatment decisions.

PURPOSE The association between epithelial to mesenchymal transition in High Grade Serous Ovarian Cancer (HGSOC) and poor prognosis is known. However, molecularly defining a subset of tumours that reproducibly associates with poor prognosis has been an elusive goal in this disease. A molecular signature that can robustly identify patients with poor prognosis and guide treatment decisions, including surgical strategy and targeted therapies, can improve survival rates. EXPERIMENTAL DESIGN We carried out RNA sequencing of 139 tumour samples (Brescia cohort), an external validation on 362 and 126 patients from the Scottish and Garsed cohort, respectively; and meta-analysis of 1023 tumours to develop clinically useful risk groups. Identification of therapeutic targets was carried out by transcriptomic analyses of FLOW-sorted tumour epithelial cells from fresh tumours and multiplex IF assessment of tissue sections. RESULTS In this study we have validated the prognostic strength of the OxC-EMT in three independent patient cohorts- Brescia [HR=3.6 (95% CI=1.59-7.97), p=1.99e-03], Scottish [HR=1.71 (95% CI=1.08-2.70), p=2.23e-02] and Garsed [Kruskal-Wallis p=0.00071]. OxC-based risk-stratification of HGSOC can robustly identify poor risk patients with a 5-year median survival for OxC-EMT-high and OxC-EMT-low risk groups of 13% and 50%, respectively (95%CI: 7.1%-23.5% vs. 36.1%-69.3%) in the Brescia cohort. Further analysis of the risk groups suggests that an alternate surgical strategy and a combination therapy involving EMT targeting drugs and immunomodulators could elicit improved clinical response in poor risk patients. CONCLUSIONS This study provides a clinically useful risk stratification strategy for HGSOC as well as targeted treatment options for high-risk patients.