Enhanced predictive value of KELIM for surgical resectability in HRD-positive high-grade serous ovarian cancer.

Abstract

5590 Background: Neoadjuvant chemotherapy followed by interval debulking surgery is commonly used in the management of advanced ovarian cancer. However, there is currently no reliable tool to predict the likelihood of achieving complete cytoreduction after 3–4 cycles of chemotherapy. Surgical outcomes are classified as R0 (no residual disease), R1 (residual lesions <1 cm), or R2 (residual disease ≥1 cm). The KELIM index, calculated from CA-125 kinetics during chemotherapy, has emerged as a potential biomarker of tumor regression and chemosensitivity in advanced ovarian cancer. We aim to study the performance of KELIM score as predictor of complete cytoreduction. Methods: This single-center, retrospective study included 69 patients with advanced high-grade serous ovarian cancer (Stage III/IV) who underwent interval cytoreductive surgery following neoadjuvant chemotherapy between January 2020 and December 2025. Kelim index values were calculated using Biomarker-Kinetics and categorized as favorable (≥1) or unfavorable (<1) as per literature. Further, ROC curve analysis was performed to identify the optimal KELIM cutoff for predicting complete cytoreduction. Correlations with degree of cytoreduction (R0, R1, R2) were analyzed using comparative statistics. Associations with molecular markers (BRCA, HRD) were also explored. Results: The median age of patients was 62 years [IQR 57–70]. The median KELIM score was 0.85 [IQR 0.69-1.00]. KELIM demonstrated statistically significant predictive performance for R0, with an area under the curve (AUC) of 0.69 (95% CI, 0.56–0.82; p = 0.004). The AUC optimal cutoff was KELIM = 0.995, yielding a sensitivity of 53.9% and specificity of 92.6%. Notably, this value closely aligns with the cutoff reported in the literature (KELIM = 1.0), which in our cohort corresponded to a sensitivity of 51.3% and specificity of 96.3% (Youden index = 0.47). Additional analyses were conducted using the literature-defined cutoff of KELIM = 1.0. Patients were categorized into two groups: Group A (22 patients) with favorable (≥1) and Group B (47 patients) with unfavorable (<1) KELIM scores. Patients with a favorable KELIM were significantly more likely to achieve complete cytoreduction compared with those with an unfavorable KELIM (R0: 95.2% vs 41.3%, p < 0.001). The discriminative performance of KELIM was numerically higher in HRD-positive patients AUC 0.706 (95% CI, 0.28-1) compared with HRP patients AUC 0.563 (95% CI, 0-1). KELIM was associated with degree of cytoreduction: Median 1 [0.71-1.20] for R0, 0.79 [0.70-0.88] for R1, and 0.64 [0.48-0.70] for R2, p=0.019. Conclusions: KELIM is a good predictor of complete resectability in high grade serous ovarian cancer. The differential predictive performance among the HRD status should be further explored.