Association of adjuvant chemotherapy regimen with serial CA-125 kinetics (KELIM framework) and progression-free survival after cytoreductive surgery for ovarian cancer: a retrospective cohort study

Abstract Objectives Serum CA-125 remains a cornerstone biomarker in ovarian cancer surveillance; however, the prognostic significance of serial postoperative CA-125 kinetics across histological subtypes remains incompletely defined. This study evaluated longitudinal CA-125 patterns following adjuvant chemotherapy and their association with progression-free survival (PFS) in patients undergoing cytoreductive surgery. Methods In this retrospective cohort study, 126 women (≥18 years) with histologically confirmed ovarian cancer treated between 2015 and 2024 at a tertiary center (King Abdulaziz University Hospital) were included. All patients underwent primary cytoreductive surgery followed by adjuvant chemotherapy. Residual disease was categorized as optimal (≤1 cm) or suboptimal (>1 cm). Tumor characteristics were classified according to FIGO and WHO criteria. Serum CA-125 was measured at baseline and approximately 3 and 6 months postoperatively. Median CA-125 values were compared across histological subtypes using the Kruskal-Wallis test. PFS was assessed using Kaplan-Meier analysis and multivariable Cox regression, adjusting for key clinicopathological variables. Results The mean age was 53.2 ± 15.5 years, and serous carcinoma was the predominant subtype (46 %). Most patients presented with advanced-stage disease. Baseline CA-125 levels were elevated in 74.6 % of patients and differed significantly across histological groups (p<0.001). CA-125 levels declined substantially by 3 months after chemotherapy, with no significant inter-subtype differences at 3 months (p=0.309) or 6 months (p=0.160). Platinum-taxane combination therapy demonstrated numerically longer PFS compared with carboplatin monotherapy in unadjusted analysis; however, this association was not statistically significant after multivariable adjustment (p=0.102). Conclusions Serial postoperative CA-125 measurements may provide clinically relevant insight into early treatment response following cytoreductive surgery. Prospective studies incorporating standardized kinetic modeling are warranted to refine biomarker-guided surveillance strategies.