Kelim index as predictor of treatment outcome in ovarian cancer surgery.

e17599 Background: The Kelim index, calculated from CA125 kinetics during chemotherapy, is an emerging biomarker for assessing tumor regression and chemo sensitivity in advanced ovarian cancer. This study evaluates the correlation between the Kelim index, chemotherapy response score (CRS), peritoneal regression grading score (PRGS), and both surgical and pathological peritoneal cancer index (PCI). Methods: This single-center, retrospective study included 73 patients with advanced high-grade serous ovarian cancer (Stage III/IV) who underwent interval cytoreductive surgery following neoadjuvant chemotherapy between November 2022 and December 2024. Kelim index values were calculated using Biomarker-Kinetics and categorized as favorable (≥1) or unfavorable (<1). Correlations with CRS, PRGS, and PCI were analyzed using chi-square tests, scatter plots, and ROC curves. Associations with molecular markers (BRCA, HRD) and imaging modalities were also explored. Statistical significance was defined as p < 0.05. Results: Patients with a favorable Kelim index were significantly more likely to achieve higher PRGS (Grade I/II: 83.93%, p = 0.0010) and CRS (CRS 2/3: 85.71%, p = 0.0005). ROC analysis demonstrated moderate predictive accuracy for surgical PCI (AUC: 0.72), imaging PCI (AUC: 0.69), and pathological PCI (AUC: 0.74). Scatter plots indicated a positive correlation between pathological PCI and the Kelim index. No significant associations were observed between the Kelim index and BRCA or HRD status (p > 0.65). Conclusions: The Kelim index correlates strongly with CRS and PRGS, underscoring its utility as a preoperative predictor of chemotherapy response and tumor regression. However, subjective differences in surgical PCI assessments limited its correlation with the Kelim index.