Objective:

To develop an integrated Body Composition and Immunonutritional Signature (BCIS) to predict pathological response, immune-related adverse events (irAEs), and survival in patients with locally advanced gastric cancer receiving neoadjuvant PD-1 inhibitor plus SOX or XELOX chemotherapy.

Approach:

• BCIS Development: BCIS was created as a 0–10 additive score based on ten prespecified adverse host features derived from pretreatment CT body composition and routine blood markers, determined through clinical assessment.

Key Findings:

• BCIS classified patients into favorable (33.8%), intermediate (42.1%), and unfavorable (24.2%) groups.
• Major pathological response (MPR) rates were 64.2%, 39.6%, and 21.8% across BCIS strata (P-trend<0.001).
• Each BCIS point reduced the odds of MPR by approximately 40% (adjusted OR = 0.61, P<0.001) and of pCR by nearly half (adjusted OR = 0.55, P<0.001).
• Adding BCIS to clinical baseline increased AUC for MPR from 0.597 to 0.710 (DeLong P<0.001).
• Each BCIS point increased the hazard of progression by 53% (adjusted HR = 1.53, P<0.001) and of death by 38% (adjusted HR = 1.38, P<0.001).

Interpretation:

BCIS is associated with pathological response and survival in patients undergoing neoadjuvant PD-1-based immunochemotherapy, providing predictive value beyond traditional tumor biomarkers.

Limitations:

• The study is retrospective and conducted in a single region, which may limit generalizability.
• Potential biases inherent in retrospective studies should be considered.

Conclusion:

BCIS could inform prehabilitation, toxicity surveillance, and shared decision-making due to its reliance on routine pretreatment workup.