Prognostic Value of Immunonutritional Status and Radiologic Muscle Mass in Older Patients Receiving Immune Checkpoint Inhibitors: A Real-World Study

Background: Identifying biomarkers for biological vulnerability in older patients with cancer remains challenging. We evaluated psoas muscle index (PMI) and immunonutritional indices’ association with toxicity and overall survival (OS) in patients ≥ 65 years receiving immune checkpoint inhibitors (ICIs). Methods: This retrospective study included 104 patients. Baseline sarcopenia was assessed via CT-derived PMI at the L3 level. Immunonutritional status was evaluated using the Prognostic Nutritional Index (PNI). Primary endpoint was immune-related adverse event (irAE) development; secondary endpoint was OS. Results: Median age was 71 years. Patients developing irAEs had significantly higher baseline PNI than those without (49.0 vs. 46.0, p = 0.042). OS did not differ significantly by irAE status (p = 0.859) or PMI group (p = 0.664). However, low PNI was strongly associated with poorer OS (17.0 months vs. not reached, p < 0.001). In a multivariable Cox model stratified by ICI treatment type, higher PNI remained independently associated with better OS (adjusted HR: 0.86, 95% CI: 0.81–0.93, p < 0.001). PNI correlated negatively with inflammatory markers NLR and SII. Conclusions: Baseline PNI was independently associated with OS, whereas PMI was not significantly associated with survival in this cohort. These findings support the potential prognostic utility of PNI in older patients receiving immunotherapy but should not be interpreted as demonstrating superiority over comprehensive sarcopenia assessment.