Prognostic Value of the Preoperative Prognostic Nutritional Index in Predicting Survival Outcomes After Curative Surgery for Colorectal Cancer

Background: The Prognostic Nutritional Index (PNI), calculated from serum albumin and lymphocyte count, indicates nutritional and immunological status. Its prognostic significance in colorectal cancer (CRC) is still being assessed. Methods: This retrospective study examined 489 patients who received curative resection for colorectal cancer (CRC). According to ROC analysis, patients were split into two groups: those with low PNI (<47.5) and those with high PNI (≥47.5). We compared the clinicopathological features, postoperative outcomes, and survival rates. Kaplan–Meier and Cox regression models were used to look at overall survival (OS) and disease-free survival (DFS). Results: A low PNI was strongly related to older age, having a lower BMI, hemoglobin, albumin, and lymphocyte levels (all p < 0.001). The low-PNI group had a higher early hospital mortality (4% vs. 1%, p = 0.031). Patients with low PNI had a significantly lower five-year OS and DFS (both p < 0.001). In multivariate analysis, low PNI independently predicted poor OS (HR = 0.640, p = 0.016) and DFS (HR = 0.570, p = 0.037), in addition to pathological stage, age, and perineural invasion. Conclusions: Preoperative PNI serves as an independent prognostic marker for survival in CRC. A low PNI demonstrates that a patient has low nutritional and immune reserves, which means they are more likely to have worse early and long-term outcomes. Including PNI in preoperative evaluation may help with personalized treatment plans.