Abstract Background: Ovarian cancer has a poor prognosis with a 5-year survival less than 50%, resulting > 14,000 deaths in the US annually and > 150,000 globally. Identifying prognostic biomarkers at time of diagnosis and elucidating the biological dysregulation among those who are more likely to progress after first-line treatment could inform personalized treatment strategies. Thus, we evaluated metabolites and metabolomic profiles in pretreatment blood associated with survival in women with high-grade serous ovarian cancer, the most common and most deadly histologic subtype. Method: We examined plasma metabolites in blood samples collected prior to ovarian cancer treatment in 80 high-grade serous ovarian cancer patients who participated in the PreOperative Pelvic Mass Study, a clinic-based study enrolling women undergoing surgery for a pelvic mass. Liquid chromatography tandem mass spectrometry was used to measure 524 known metabolites. We excluded metabolites with coefficient of variation ≥ 25% (n = 104), then removed metabolites with missing in > 20% of the samples (n = 3). Metabolites missing in < 20% of the samples were imputed to be half the minimum value for that metabolite, resulting in 417 unduplicated metabolites. All metabolite values were transformed to probit scores to achieve normality. Cox proportional hazard models were used to calculate the hazard ratios (HRs) and 95% confidence intervals (CIs) adjusting for age at diagnosis, body mass index (BMI), and stage. False discovery rate (FDR) was used for multiple testing correction. Metabolite set enrichment analysis (MSEA) was used to identify metabolite classes associated with prognosis. Results: Overall, none of the individual metabolites were significantly associated with survival after multiple testing correction (FDR > 0.05). However, 32 metabolites were associated with survival with p< 0.05, with 12 metabolites being associated with worse survival (HR range: 1.38 - 1.98) and 20 metabolites being associated with better survival (HR range: 0.54 - 0.73). MSEA revealed triglycerides (normalized enrichment score (NES) = 3.14), cholesteryl esters (NES = 2.43), and phosphatidylcholines (NES = 2.30) were positively associated with risk of death (FDR < 0.001). Steroids and steroid derivatives (NES = -1.93), sphingomyelins (NES = -2.45), and carnitines (NES = -2.27) were negatively associated with risk of death (FDR < 0.001). Diglycerides (NES = 1.96), lysophosphatidylethanolamines (NES = 1.72), and phosphatidylcholine plasmalogens (NES = 1.58) were positively associated and phosphatidylethanolamines (NES = -1.93) was negatively associated with risk of death with FDR < 0.05. Discussion: In this study, we explored plasma metabolites associated with mortality in high-grade serous ovarian cancer patients and observed multiple classes of lipid-related metabolites being associated with worse prognosis. Citation Format: Nan Lin, Oana A. Zeleznik, Julian Avila-Pacheco, Clary B. Clish, Allison F. Vitonis, Daniel W. Cramer, Kathryn L. Terry, Naoko Sasamoto. Pre-surgical blood metabolites associated with ovarian cancer prognosis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3682.