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

<b>Background:</b> 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. <b>Methods:</b> 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). <b>Results:</b> A low PNI was strongly related to older age, having a lower BMI, hemoglobin, albumin, and lymphocyte levels (all <i>p</i> < 0.001). The low-PNI group had a higher early hospital mortality (4% vs. 1%, <i>p</i> = 0.031). Patients with low PNI had a significantly lower five-year OS and DFS (both <i>p</i> < 0.001). In multivariate analysis, low PNI independently predicted poor OS (HR = 0.640, <i>p</i> = 0.016) and DFS (HR = 0.570, <i>p</i> = 0.037), in addition to pathological stage, age, and perineural invasion. <b>Conclusions:</b> 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.