Diagnostic Value of CA-125 and Other Tumor Biomarkers in Children with Suspected Malignancy: A Retrospective Cohort Study

<b>Background/Objective</b>: Tumor biomarkers are widely used in adult oncology, but their diagnostic value in pediatric patients remains unclear. This study aimed to evaluate the clinical significance of CA-125, CA 19-9, CA 15-3, and CEA in children evaluated for suspected malignancy. <b>Methods</b>: This retrospective study included 211 pediatric patients (0-18 years) referred to a tertiary pediatric oncology center. Serum levels of the four biomarkers were analyzed in relation to patient demographics, imaging findings, and final diagnoses. Statistical analyses included chi-square, Mann-Whitney U, Kolmogorov-Smirnov tests, and receiver operating characteristic (ROC) curve analysis. <b>Results</b>: Of the 211 patients, 35 (16.6%) were diagnosed with malignancy. Elevated CA-125 was significantly associated with malignancy (<i>p</i> = 0.002), particularly among postpubertal female patients. Imaging abnormalities were more frequent in CA-125-positive cases (<i>p</i> < 0.001) and in patients with confirmed malignancy. ROC curve analysis demonstrated that CA-125 had an area under the curve (AUC) of 0.642, indicating modest discriminatory power. No significant associations were found for CA 19-9, CA 15-3, or CEA. <b>Conclusions</b>: CA-125 may serve as an adjunctive diagnostic biomarker in pediatric oncology, particularly in postpubertal girls and when interpreted alongside imaging findings. Other markers showed limited diagnostic value. Given its low sensitivity, CA-125 is not suitable as a standalone screening test in children. Larger, multicenter prospective studies are needed to establish pediatric-specific reference ranges and validate these findings.