Development of a prognostic nomogram to guide clinical decision-making in metastatic gastric cancer: A Latin American cohort study.

325 Background: Metastatic gastric cancer (mGC) is associated with dismal outcomes, and most patients eventually receive only palliative care. Accurate prognostic models are urgently needed to individualize survival estimates, optimize therapeutic decisions, and inform trial design. Data from Latin American populations are scarce. We aimed to develop and internally validate a prognostic nomogram for 12-month overall survival (OS) in patients with mGC. Methods: We retrospectively analyzed 1,323 patients with histologically confirmed mGC treated at the Instituto Nacional de Cancerología (Mexico) between 2010 and 2022. Demographic, clinical, biochemical, and histologic data were collected. OS was estimated using the Kaplan–Meier method. Multivariate Cox regression was performed in R Studio, and independent prognostic factors were incorporated into a nomogram predicting 12-month OS. Discrimination and calibration were assessed Results: Median age was 54 years (±13.5), with 63.4% younger than 50 years; 52.5% were male. ECOG performance status was 0–1 in 71.2% of patients. Median weight loss at diagnosis was 10 kg. Anemia grade ≥2 occurred in 27.7% and hypoalbuminemia (