ObjectiveWe investigated whether pretreatment systemic inflammatory markers are associated with survival outcomes in patients with endometrial cancer (EC). MethodsData from the Japanese Gynecologic Oncology Group 2043 were analyzed. Patients who did not receive chemotherapy or were lost to follow-up were excluded. Associations of pretreatment systemic inflammatory markers, including the neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and hemoglobin, albumin, lymphocyte, and platelet (HALP) score, with progression-free survival (PFS) and overall survival (OS) were analyzed. The optimal NLR, PLR, and HALP score cutoff values for PFS and OS were determined. Survival estimates were calculated and compared using the Kaplan–Meier method and log-rank test. ResultsWe included 712 patients (median age: 55 [range, 28–74] years; body mass index [BMI]: 21.1 [15.2–38.6] kg/m2). For PFS, optimal NLR, PLR, and HALP score cutoff values were 1.48, 0.017, and 35.52, respectively, and for OS, the values were 1.88, 0.026, and 19.87, respectively. At optimal PFS-related cutoff values, NLR was associated with BMI; PLR with age, BMI, and clinical stage; and HALP score with BMI, clinical stage, and lymph node metastasis. At optimal OS-related cutoff values, NLR was associated with BMI, PLR, and BMI; the HALP score was associated with age and BMI. The HALP score was a prognostic factor for PFS (p = 0.025), while PLR and HALP scores were prognostic factors for OS (both p = 0.028). ConclusionsPretreatment systemic inflammatory markers are associated with survival outcomes in patients with EC, with the HALP score being a prognostic factor for PFS and OS.