Beyond individual markers: Prognostic value of the combined CEA/PNI score in metastatic colorectal cancer as a predictor of survival.

Malnutrition and systemic inflammation significantly worsen the prognosis of oncology patients, contributing to 10-20% of cancer-related deaths. While the Carcinoembryonic Antigen (CEA) reflects tumor burden, the Prognostic Nutritional Index (PNI) captures nutritional and immune status. This study aimed to evaluate whether the combination of CEA and PNI provides superior prognostic stratification compared to either biomarker alone in patients with metastatic colorectal cancer (mCRC). This retrospective cohort study analyzed data from 512 mCRC patients at baseline and at the first response assessment (after two months of systemic treatment). Patients were stratified into four groups based on CEA (<5 or ≥5 ng/mL) and PNI (<37.52 or ≥37.52). Overall Survival (OS) and Progression-Free Survival (PFS) were analyzed using the Kaplan-Meier method and Cox regression. Our results showed that the prevalence of PNILOW was 49.8% at diagnosis and increased to 54.4% after chemotherapy (p = 0.047). PNI and Body Mass Index (BMI) status alone were not significant predictors of OS or PFS. In contrast, CEA was a powerful indicator, with CEAHIGH consistently predicting worse OS and PFS. Crucially, the combined CEA/PNI score provided the strongest discrimination. Patients with the high-risk profile (CEAHIGH/PNILOW) had a significantly increased risk of death (HR 2.41, p = 0.01) and progression (HR 2.30, p < 0.01) at baseline, compared to the lowest-risk group (CEALOW/PNIHIGH). This elevated risk was maintained at the first assessment (HR 2.30, p < 0.01 for death and HR 6.81, p < 0.01 for progression). We conclude that PNI alone is insufficient to predict survival in mCRC patients. However, its integration with CEA creates a robust, easily obtainable biomarker that provides superior prognostic stratification by combining information on tumor burden and host systemic status.