Prognostic Significance of the Ki-67 Index with an Optimal Cut-off Value of 32.5% in Uterine Sarcoma and Uterine Carcinosarcoma: A Retrospective Cohort Study.

Objective: Uterine sarcomas and uterine carcinosarcomas are rare heterogeneous malignancies with poor prognosis. Though carcinosarcomas have been pathologically reclassified as dedifferentiated endometrial carcinomas, their highly aggressive clinical behavior merits combined analysis with uterine sarcomas. This study aimed to investigate the prognostic value of Ki-67 proliferation index in major histologic subtypes and identify an optimal cut-off value for risk stratification. Materials and Methods: We retrospectively enrolled 86 surgically treated primary uterine sarcoma and carcinosarcoma patients (2006-2019). Ki-67 labeling index was detected via immunohistochemistry. The optimal cut-off value for Ki-67 was determined using receiver operating characteristic (ROC) curve analysis. Overall survival (OS) and progression-free survival (PFS) were evaluated via Kaplan-Meier curves and Cox regression. Results: The optimal Ki-67 cut-off value was 32.5%. High Ki-67 expression (≥32.5%) was significantly associated with older age (P=0.001), postmenopausal status (P=0.002), and aggressive histological subtypes 0.760 (P<0.001). High Ki-67 group had worse 3-year PFS (18.5% vs 76.4%) (range, 22-73) and 3-year OS (25.5% vs 85.4%). Multivariate analysis confirmed high Ki-67 as an independent prognostic factor for poorer PFS and OS (P < 0.001). Larger tumor size (P < 0.001), postmenopausal status (PFS: P = 0.001; OS: P = 0.002), and high-risk histological type (P < 0.001) also remained significant. Notably, the 32.5% cut-off applies across major histological subtypes. Conclusion: Ki-67 index serves as an independent biomarker for uterine sarcoma and carcinosarcoma. The 32.5% cut-off effectively divide patients into low- and high-risk groups, with the latter demonstrating significantly inferior survival outcomes.