842 Outcomes in mucinous ovarian/fallopian tube cancer (MOC); real world outcomes from two tertiary London centres

Introduction/Background MOC is a rare form of epithelial ovarian cancer, most frequently presenting at an early stage. We investigated real-world outcomes in this rare pathology across two tertiary centres. Methodology Patients with a diagnosis of MOC treated at University College London and St Bartholomew's Hospitals between 2009–2021 were identified and data collected. Calculations were performed using Prism v9.5.1; p=<0.05 was considered significant. Results 90 patients were identified; FIGO I n=67 (75%), II n=12 (13%), III n=9 (10%), IV n=1 (1%); unknown n=1 (1%). Tumour grade(G)1 n=24 (27%), G2 n=43 (48%) and G3 n=11 (12%); unknown n=2 (2%). Median age 51 years (21–97); 88/90 (98%) had primary surgery; 2/90 (2%) inoperable. 51 patients had documented appendectomy; 1/51 (2%) with serosal involvement. 33 patients had systemic anti-cancer therapy (SACT); carboplatin/paclitaxel n=26 (79%); single agent carboplatin n=3 (10%) and FOLFOX/CAPOX n=4 (12%). Long term survival data available for 88 patients; 2 lost to follow-up. Relapse rate (RR); FIGO I 10/65 (15%), II 1/12 (8%), III 8/9 (89%) and IV 1/1 (100%). RR for FIGO I G3 was 3/6 (50%), significantly higher (p=0.0072) compared to G1 1/28 (4%) but not G2 disease 6/32 (19%). 9/61 (15%) FIGO I G1/G2 disease received SACT with no significant difference in RR p=0.06. For FIGO I/II disease, median progression free survival (mPFS) and overall survival (mOS) not reached; III mPFS 10 months and mOS 33 months; IV mPFS 6 months and OS 6months. Conclusion We found MOC most frequently presented with FIGO I/II disease which, alongside tumour grade, inferred a better prognosis. We found no benefit from SACT in reducing relapse in early-stage low grade tumours. Patients with advanced stage disease are likely to recur with a short mPFS and mOS reflecting the need for further research to SACT options in this population. Disclosures See attached COI forms.