Objective: Associations between hospital treatment volume and survival outcomes for women with 3 types of gynecologic malignancies, and the trends and contributing factors for high-volume centers were examined. Methods: The Japan Society of Obstetrics and Gynecology tumor registry databased retrospective study examined 206,845 women with 80,741, 73,647, and 52,457 of endometrial, cervical, and ovarian tumor, respectively, who underwent primary treatment in Japan between 2004 and 2015. Associations between the annual treatment volume and overall survival (OS) for each tumor type were examined using a multivariable Cox proportional hazards model with restricted cubic splines. Institutions were categorized into 3 groups (low-, moderate-, and high-volume centers) based on hazard risks. Results: Hazard ratio (HR) for OS each the 3 tumors decreased with hospital treatment volume. The cut-off points of treatment volume were defined for high-(≥50, ≥51, and ≥27), moderate-(20–49, 20–50, and 17–26), and low-volume centers (≤19, ≤19, and ≤16) by cases/ year for endometrial, cervical, and ovarian tumors, respectively. Multivariate analysis revealed younger age, rare tumor histology, and initial surgical management as contributing factors for women at high-volume centers (all, p<0.001). The proportion of high-volume center treatments decreased, whereas low-volume center treatments increased (all p<0.001). Treatment at high-volume centers improved OS than that at other centers (adjusted HR [aHR]=0.83, 95% confidence interval [CI]=0.78–0.88; aHR=0.78, 95% CI=0.75–0.83; and aHR=0.90, 95% CI=0.86–0.95 for endometrial, cervical, and ovarian tumors). Conclusion: Hospital treatment volume impacted survival outcomes. Treatments at high-volume centers conferred survival benefits for women with gynecologic malignancies. The proportion of treatments at high-volume centers have been decreasing recently.
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