OBJECTIVE:To examine the incidence and prognostic effects of intraoperative capsule rupture and to assess the effectiveness of postoperative chemotherapy for intraoperative tumor rupture in apparent stage I epithelial ovarian cancer.METHODS:This is a society-based retrospective observational study in Japan that examined 15,163 women with stage IA-IC1 epithelial ovarian cancer who underwent primary surgical treatment between 2002 and 2015. Associations between intraoperative capsule rupture and cause-specific survival, and between postoperative chemotherapy and cause-specific survival among intraoperatively ruptured cases were examined by histology type (clear cell n=6,107, endometrioid n=3,910, mucinous n=3,382, and serous n=1,764).RESULTS:Clear cell histology had the highest risk of intraoperative capsule rupture (57.3%), followed by endometrioid (48.8%), serous (41.8%), and mucinous (32.0%) histologies (P<.001). On multivariable analysis, clear cell type exhibited the largest effect of intraoperative capsule rupture on cause-specific survival (adjusted hazard ratio [HR] 1.99, 95% CI 1.45-2.75), followed by serous (adjusted HR, 1.61, 95% CI 0.84-3.11), mucinous (adjusted HR 1.28, 95% CI 0.79-2.09), and endometrioid (adjusted HR, 1.14, 95% CI 0.64-2.01) tumors. Postoperative chemotherapy for intraoperatively ruptured cases did not improve cause-specific survival in any histologic types in multivariable analysis: clear cell, adjusted HR 0.86, 95% CI 0.56-1.31; serous, adjusted HR 1.08, 95% CI 0.42-2.74; mucinous, adjusted HR 1.11, 95% CI 0.55-2.27; and endometrioid, adjusted HR 2.81, 95% CI 0.85-9.30 (all, P>.05). In the cohort-level analysis of ruptured cases (n=7,227), postoperative chemotherapy use has significantly decreased in mucinous (16.3% relative decrease), endometrioid (13.1% relative decrease), and clear cell (9.3% relative decrease) (all, P<.05); but, the cohort-level 5-year cause-specific survival rate did not change over time (all, P>.05).CONCLUSION:Among apparent stage I epithelial ovarian cancer, the clear cell type possesses a disproportionally high risk of capsule rupture during adnexectomy and is associated with the most adverse effect on survival. A decrease in the use of postoperative chemotherapy for intraoperatively ruptured cases in Japan is likely the result of increasing awareness of the absence of survival benefits.
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