Abstract
BACKGROUND: The accumulation of ascites is a major symptom of ovarian cancer. The volume of ascites is a pathophysiological indicator of the peritoneal environment, such as inflammation and fibrosis; however, the relationship between the volume of ascites and oncological outcomes remains unclear. We herein retrospectively examined the effects of the volume of ascites on the prognosis of epithelial ovarian cancer in a multi-institutional large cohort using the stratification of clinical characteristics and statistical adjustment methods. METHODS: Of 5,268 patients with ovarian tumors in the Tokai Ovarian Tumor Study Group between 1986 and 2020, we included 1,966 cases of epithelial ovarian cancer and examined the relationship between the volume of ascites at the initial surgery and the prognosis of patients. We performed a multivariate analysis and propensity score weighting for covariate adjustments to precisely estimate the prognostic impact of ascites accumulation. A subgroup analysis was also performed to examine differences in the prognostic implications of ascites accumulation among histotypes. RESULTS: A reservoir of 100 mL of ascites was confirmed as the cut-off value in our cohort. A Kaplan-Meyer analysis with propensity score adjustments indicated that the accumulation of more than 100 mL of ascites shortened overall survival. The multivariate analysis revealed that the increased accumulation of 100 mL of ascites was an independent prognostic factor for overall survival (HR 1.242; 95% CI 1.050-1.470; P = 0.012). The subgroup analysis showed the prognostic significance of ascites accumulation in mucinous and endometrioid histologies. CONCLUSIONS: The accumulation of even a low to intermediate volume of ascites (≥ 100 mL) was confirmed to be an independent poor prognostic factor in epithelial ovarian cancer. Furthermore, its prognostic impact differed among histotypes.