Diagnostic Performance of Contrast-Enhanced Computed Tomography in Predicting Lymph Node Metastasis in Epithelial Ovarian Cancer: The Added Value of Combining CT with CA-125

Background/Objectives: Preoperative prediction of retroperitoneal lymph node (LN) metastasis in epithelial ovarian cancer (EOC) may inform surgical planning and counselling. We evaluated the diagnostic performance of contrast-enhanced computed tomography (CT) for pathological LN metastasis and explored whether adding serum CA-125 to CT findings improves prediction. Methods: This single-centre retrospective diagnostic accuracy study included 97 patients with invasive EOC who underwent primary (n = 81) or interval (n = 16) cytoreductive surgery with histopathological LN assessment (2022–2025) and CT within two months before surgery. Pelvic and para-aortic CT findings were compared with histopathology at the patient and regional levels. A logistic model combining these CT findings with log2-transformed CA-125 was compared with the CT-only model using a likelihood-ratio test and was internally validated by bootstrapping. Results: Pathological LN metastasis was present in 31 patients (32.0%). At the patient level, CT had a sensitivity of 58% and a specificity of 67%; a short-axis threshold of >10 mm increased specificity to 94% (sensitivity 23%). Adding CA-125 to the CT model improved model fit (likelihood-ratio p = 0.019) and discrimination (optimism-corrected area under the curve 0.63 vs. 0.70), with acceptable calibration (corrected slope 0.86). The association of CA-125 with LN metastasis was attenuated after adjustment for high-grade serous histology (adjusted odds ratio per doubling 1.18, 95% confidence interval 0.98–1.43) and was not evident in patients with stage III–IV disease. Conclusions: CT has limited sensitivity for LN metastasis in EOC, although enlarged nodes are highly specific. CA-125 may add information to CT findings, but this largely reflects differences in disease extent and histology. These preliminary findings require prospective, externally validated studies before any clinical application.