Preoperative prognostic nutritional index in prediction of surgical complications and oncological outcomes in retroperitoneal sarcoma.

Nutritional status is a potentially modifiable factor influencing outcomes in retroperitoneal sarcoma (RPS), yet reliable preoperative markers remain underexplored. The prognostic nutritional index (PNI), which combines serum albumin and lymphocyte count, may offer a simple, reproducible tool for risk stratification. We conducted a retrospective cohort study of adult patients undergoing curative-intent resection of primary or recurrent RPS between 2020 and 2024 at a Latin American tertiary center. Patients were stratified by a PNI cutoff of 40, derived via ROC analysis. The primary endpoint was the incidence of major postoperative complications (Clavien-Dindo ≥ III), while secondary endpoints included overall survival (OS) and recurrence-free survival (RFS). Multivariable logistic and Cox regression models were used to assess independent predictors. Among 142 patients, 52.1% had a low PNI (≤ 40). Major complications occurred in 27.6% of patients and were significantly more freq uent in the low-PNI group (37.8% vs. 16.2%, p = 0.006). Low PNI independently predicted significant morbidity (OR 2.72, 95% CI 1.18-6.29, p = 0.018), alongside operative time and intraoperative transfusion. After a median follow-up of 39 months, low PNI was associated with inferior 3-year OS (55% vs. 74%, p = 0.008) and RFS (44% vs. 63%, p = 0.022). On multivariable analysis, low PNI remained a significant predictor of OS (HR 1.98, p = 0.019) and RFS (HR 1.67, p = 0.037). A preoperative PNI ≤ 40 identifies RPS patients at increased risk for significant complications and inferior survival, independent of tumor grade or surgical extent. These findings remained consistent across sensitivity analyses restricted to primary RPS, support the integration of PNI into perioperative risk stratification and nutritional optimization strategies.