391 Outcome and prognostic factors of low-grade serous ovarian cancers: an observational retrospective study

Introduction/Background Low-grade serous ovarian cancer (LGSOC) is a very rare histological subtype of serous ovarian cancer, representing approximately 2% of all epithelial ovarian cancers. LGSOC has a better prognosis and a low response rate to chemotherapy in comparison to high-grade serous ovarian carcinoma (HGSOC). Methodology A retrospective review of the medical records of all patients with histologically proven LGSOC diagnosed and treated between January 2003 and December 2019. Results Twenty-three patients diagnosed with LGSOC and treated in KFSHRC were identified. The median age at diagnosis was 45.5 years (range 26–66). Median BMI was 26.1 (range 18–43). Twenty-one (91.3%) patients had de novo LGSOC; however, only two patients (8.7%) had been transformed and recurred from SBOT. The median BMI was 26.1 (18–46). Eight patients (34.7%) had FIGO stage IV at diagnosis, but 3 (13%),3 (13%), and 9(39%) had stages I, II, and III, respectively. Ten patients (43.8%), 5 (21.7%), and 3 (13%) had complete response (CR), stable disease (SD), and partial response (PR) after first-line therapy, respectively. At a median follow-up of 34 months (95% confidence interval (CI): 25.32–42.69), the median PFS was 75.2 months (95% CI: 17.35–133.05), and the median OS was not reached. Conclusion LGSOC has better PFS and OS as compared to high-grade ovarian cancer. There is systemic treatment (chemotherapy or hormonal therapy). Optimal cytoreduction is associated with better PFS and OS than suboptimal debulking. The optimal systemic chemotherapy or hormonal treatment is still controversial. Disclosures All the authors have nothing to disclose.