LAUSR

Results: Total of 74/84 samples were successfully profiled. Median age at diagnosis was 53 yrs. 41 (55.4%) were stage 1, 7 (9.5%) stage 2, 24 (32.4%) Stage3, 2 (2.7%) stage 4. 64/74 (86.5%) of pts received adjuvant chemotherapy post debulking surgery with 38% recurrence rate (median PFS 27 months (m)). Median follow up was 36m. Based on irGES, 4 distinct molecular subgroups of OCCCs were identified. G1 was hallmarked by high NK cell markers/PD-1 expression, G2 by increased CTLA-4/PD-L1 expression, G3 by adhesion cell markers, and G4 by increased levels of pro angiogenic genes. G1 was observed to have significantly poorer PFS (median PFS 20m vs 68m, p1⁄4 0.011) and a trend towards poorer OS when compared with G2/3/4 (median OS 38.8m vs undefined, p1⁄4 0.0501). G4 carried the best prognosis (median PFS 108m vs 26m, p1⁄4 0.0515; median OS undefined, p1⁄4 0.0726). This difference in OS and PFS was reflected in stage 1 pts (p< 0.02 and<0.05; respectively) with a similar trend observed but not significant in non-stage 1 pts. Significant correlation was observed between gene and protein expression of tumour PD-1, tumour and stromal PD-L1, and tumour IL-6 using IHC (p< 0.0001 for all comparisons). 6 (8.1%) pts were MMR deficient with no significant association between ARID1A and MMR expression across each irGES.