DIAGNOSTIC VALUE OF THE CA-125/CEA RATIO FOR DIFFERENTIATING PRIMARY OVARIAN CARCINOMA FROM GASTROINTESTINAL MALIGNANCIES IN A TERTIARY GYNECOLOGIC ONCOLOGY CENTER IN NORTH MACEDONIA

Abstract

Background: Differentiating primary ovarian carcinoma from gastrointestinal (GI) malignancies is challenging. The CA-125/CEA ratio, with a cut-off around 25:1, may help distinguishing ovarian from non-ovarian cancers. We evaluated the performance of CA-125, CEA, and their ratio in women treated at a tertiary gynecologic oncology center in North Macedonia.

Methods: A prospective study of 72 women ≥18 years with adnexal masses, ascites, or elevated tumor markers suspicious for malignancy, treated surgically between 2019-2024. Preoperative serum CA-125, CEA, CA19-9, and CA72-4 were measured, and the definitive diagnosis was established histopathologically. Cases were classified as ovarian/gynecologic or GI malignancies. The primary endpoint was the ability of the CA-125/CEA ratio to differentiate ovarian from GI malignancy.

Results: The median age was 61 years, and 79.2% of patients were postmenopausal. Ovarian/gynecologic malignancy was diagnosed in 69/72 (95.8%), and 3/72 (4.2%) had GI malignancies. The CA-125/CEA ratio was significantly higher in ovarian malignancies (101.0 vs 11.4, p=0.033). A cut-off of ≤25 identified all 3 GI cancers (100% sensitivity), but misclassified 15 ovarian cancers (72.7% specificity). The ROC AUC was 0.86 for the CA-125/CEA ratio, compared to 0.61 for CA-125 alone.

Conclusions: A CA-125/CEA ratio ≤25 identified GI malignancies with high sensitivity but modest specificity. This approach may reduce unnecessary GI endoscopies in resource-limited settings like North Macedonia, though larger studies are needed.