[Analysis of the efficacy and influencing factors of immunotherapy in gastric cancer liver metastasic patients].

<b>Objective:</b> To explore the efficacy and factors affecting the treatment of gastric cancer liver metastasis (GCLM) with immune checkpoint inhibitors (ICI). <b>Methods:</b> This is a retrospective cohort study. Clinical and pathological data of 588 patients with GCLM treated at the Department of General Surgery, First Medical Center, People's Liberation Army General Hospital, from January 2018 to December 2022 were retrospectively collected. There were 491 males and 97 females, aged (<i>M</i>(IQR)) 60(14) years (range: 18 to 86 years). Patients were divided into an ICI treatment group (<i>n</i>=142) and a non-ICI treatment group (<i>n</i>=446) based on whether they received ICI therapy. Clinical and pathological data between the two groups were compared using the <i>χ</i>² test or Mann-Whitney <i>U</i> test. Propensity score matching (PSM) was performed with cT stage, cN stage, surgical treatment, targeted therapy, and biomarkers as covariates, using a 1∶1 nearest neighbor matching method with a caliper value of 0.2. Univariate and multivariate analyses were conducted using Cox proportional hazards regression models, with relevant variables selected through forward stepwise regression. Survival curves were plotted using the Kaplan-Meier method, and group differences were compared using the Log-rank test. Subgroup analysis was conducted to identify potential beneficiary populations for ICI through forest plots. <b>Results:</b> After PSM, 114 patients were included in each group, and there were no statistically significant differences in the baseline data between the two groups (all <i>P</i>>0.05). The results of Cox multivariate analysis after PSM showed that cN2-3 stage (<i>HR</i>=1.348, 95%<i>CI</i>: 1.091 to 1.665, <i>P</i>=0.006) and peritoneal metastasis (<i>HR</i>=1.877, 95%<i>CI</i>:1.360 to 2.590, <i>P</i><0.01) were independent risk factors for survival in GCLM patients; radical surgery (<i>HR</i>=0.391, 95%<i>CI</i>: 0.305 to 0.501, <i>P</i><0.01), immunotherapy (<i>HR</i>=0.630, 95%<i>CI</i>: 0.503 to 0.788, <i>P</i><0.01), and deficient DNA mismatch repair (dMMR) or combined positive score (CPS)≥5 (<i>HR</i>=0.454, 95%<i>CI</i>: 0.320 to 0.644, <i>P</i><0.01) were independent protective factors for survival in GCLM patients. After PSM, the overall survival was 12.4 (13.0) months in the non-immunotherapy group and 17.6 (17.8) months in the immunotherapy group (Log-rank test:<i>P</i>=0.029). Subgroup analysis showed that female patients, those with primary tumors located in the upper stomach, cN2-3 stage, one liver metastasis, synchronous liver metastasis, receiving targeted therapy, and those with dMMR or CPS≥5 were more likely to benefit from ICI therapy (all <i>P</i><0.05). <b>Conclusions:</b> ICI prolongs overall survival in GCLM patients. Female patients, those with primary tumors located in the upper stomach, cN2-3 stage, one liver metastasis, synchronous liver metastasis, receiving targeted therapy, and those with dMMR or CPS≥5 are more likely to benefit from ICI therapy.