Impact of triglyceride-glucose index on the long-term prognosis of advanced gastric cancer patients receiving immunotherapy combined with chemotherapy

BACKGROUND Gastric cancer (GC) is the fifth most common malignancy and the third leading cause of death worldwide. Despite advancements in immunotherapies, patient prognosis remains poor, necessitating the identification of key prognostic factors to optimize the treatment approaches. Insulin resistance, as indicated by the triglyceride glucose (TyG) index, is increasingly recognized for its impact on cancer progression and immune modulation, and its potential role in GC prognosis is of particular interest. AIM To investigate whether the TyG index, a surrogate marker of insulin resistance, can predict the prognosis of patients with advanced GC receiving immunotherapy combined with chemotherapy. METHODS This retrospective study included 300 patients with advanced GC who received sintilimab combined with chemotherapy. The patients were categorized into two groups according to high or low TyG index, and independent prognostic factors for overall survival (OS) were determined using Cox proportional hazards regression analysis, which led to the development of a nomogram model. RESULTS Of the included patients, 136 had a high TyG index and 164 had a low TyG index. The median progression-free survival of the high TyG index group was significantly longer than that of the low TyG index group. Similarly, the median OS of the high TyG index group was significantly longer than that of the low TyG index group. The objective response and disease control rates in the two groups were 18.38% vs 9.15% and 58.82% vs 46.95%, respectively. No significant difference was noted in the incidence of adverse reactions at any level between the two groups (P > 0.05). In multivariate analysis, the Eastern Cooperative Oncology Group score, programmed cell death ligand 1 expression, and TyG index acted as independent prognostic factors for OS. Of these factors, the hazard ratio of the TyG index was 0.36 (95% confidence interval: 0.36-0.55, P < 0.001), and the nomogram model re-emphasized its importance as the main predictor of patient prognosis, followed by programmed cell death ligand 1 expression and the Eastern Cooperative Oncology Group score. CONCLUSION The TyG index is a long-term predictor of the efficacy of immunotherapy combined with chemotherapy, and patients with a high index have a better prognosis.