1043 Prognostic factors and survival in non-epithelial ovarian cancer: a nationwide population-based Swedish gynaecologic cancer group (SweGCG) study

Introduction/Background Non-epithelial ovarian cancer (NEOC) accounts for 6% of all ovarian cancer in Sweden and are divided into germ cell tumours (GCTs), sex cord-stromal tumours (SCSTs) and other more uncommon subtypes. Only a few population-based studies of NEOC have been published. The aim of this study was to provide additional knowledge about these rare tumours by analysing population-based high-validity Swedish register data. Methodology All women with NEOC registered in the Swedish Quality Registry for Gynecological Cancer between 2008 and 2022 were included. Cox proportional hazard was used in survival analyses. Results 718 patients were diagnosed with NEOC; 187 with GCTs, 459 with SCSTs, and 72 with other subtypes. Median age at diagnosis was 32 years for GCTs (range 18–83) and 57 years (range 18–93) for SCSTs. Although most patients were diagnosed at FIGO stage I (GCTs: 73.2%; SCSTs: 85.8%), the primary tumour was often ≥10 cm (GCTs: 74.0%; SCSTs: 55.0%). The majority of patients underwent primary surgery. Macroscopic radicality was achieved in 96.5% and 97.6% of the GCT and SCST patients, respectively. Most young GCT patients had fertility sparing surgery. After a median follow-up of 5.6 years (GCT; range 0.1–15.2 years) and 6.6 years (SCST; range 0.1–15.4 years), 89.6% of GCT and 91.8% of SCST patients were cancer free. Overall survival was 89.8% for GCT and 88.2% for SCST patients. Age ≥35 years at diagnosis was associated with worse survival in GCTs HR 24.3, 95%CI 3.25–182.2. Higher age at diagnosis was also associated with worse survival in SCSTs per year: HR 1.08, 95%CI 1.06–1.11. Advanced stage was associated with worse prognosis in both GCTs and SCSTs e.g. SCSTs stage III versus stage I: HR 11.32, 95%CI 5.26–24.33. Conclusion The overall survival was high in this population-based study of NEOC in Sweden. Higher age at diagnosis and advanced stage were adverse prognostic factors. Disclosures Nothing to disclose.