Impact of prognostic nutritional index on oncological outcomes and mortality among advanced gastric cancer patients: European GASTRODATA registry analysis.

While Prognostic Nutritional Index (PNI) is an established predictor of outcomes in Asian gastric cancer (GC) patients, data among Western populations are limited. This study assessed the predictive value of PNI in European GC patients undergoing multimodal treatment. Data from GASTRODATA, the largest European repository of GC patients undergoing gastrectomy, were collected between 2017 and 2022. The primary outcome was textbook outcome (TO) achievement, and the secondary was 90-day mortality. PNI was calculated one day before surgery, with a cut-off of 45.5 based on ROC analysis. Among 721 patients included 60.7% were men. Most patients had advanced tumors (cT3-4 = 75.2%) and metastatic lymph nodes (57.7%). Neoadjuvant chemotherapy (NAC) was administered to 46.7% of patients, and 32.9% received adjuvant chemotherapy. Median PNI was 49.5 (IQR 45.0-56.4). Low PNI was present among 30% of patients and was associated with decreased odds of TO achievement (OR = 0.57, 95% CI 0.37-0.89), higher 90-day mortality (OR = 4.99, 95% CI 2.32-10.73). NAC administration was associated with lower morbidity risk (OR = 0.56, p = 0.0408), and low PNI was a predictor of receiving AC (p = 0.0005). PNI was a valuable predictor for oncological outcomes and morbidity among European GC patients undergoing multimodal. While low PNI was associated with decreased odds of TO achievement and increased risk of 90-day mortality, further prospective and nutritional intervention studies are warranted to standardize the PNI threshold and improve its clinical applicability.