Prognostic Associations of BMI and Metabolic Syndrome With Outcomes After Anti-PD-1 Therapy in Recurrent or...

To evaluate the associations of body mass index (BMI) and metabolic syndrome (MetS) with outcomes in patients with recurrent or metastatic nasopharyngeal carcinoma (R/M-NPC) receiving anti-PD-1 therapy, and to develop a prognostic model for overall survival (OS). This multicenter retrospective study included 238 patients with BMI ≥ 18.5 kg/m² from two Chinese hospitals. BMI and MetS associations were evaluated using center-adjusted, center-stratified, hierarchical, and quantitative sensitivity analyses. An OS nomogram was developed in the Xiangya cohort and externally evaluated in the Harbin cohort. In clinical confounder-adjusted models with the exposures entered separately, high BMI was associated with OS (HR, 0.462; 95% CI, 0.324-0.657) and PFS (HR, 0.511; 95% CI, 0.380-0.688), and MetS was associated with OS (HR, 0.433; 95% CI, 0.278-0.674) and PFS (progression-free survival) (HR, 0.616; 95% CI, 0.439-0.866). When BMI and MetS were jointly modelled, the MetS-PFS association was attenuated (HR, 0.714; 95% CI, 0.504-1.012; p = 0.058). Exploratory biomarker analyses revealed group differences in combined positive score (CPS) and pan-immune-inflammation value (PIV). Center-specific effect directions were consistent, but the external-center calibration slope was 0.53 (95% CI, 0.08-0.98). Among anti-PD-1-treated Chinese patients with R/M-NPC and a BMI ≥ 18.5 kg/m², higher BMI and MetS showed prognostic associations. These observational data do not establish causal or treatment-predictive effects, and prospective validation in non-Chinese populations across the full body-weight spectrum is needed.