Effect of liver metastasis on the efficacy of immune checkpoint inhibitors in cancer patients: a systemic review and meta-analysis

Liver metastasis is a frequent phenomenon in advanced tumor disease. Immune checkpoint inhibitors (ICIs) are a new class of therapeutics that can improve the prognosis of cancer patients. The purpose of this study is to elucidate the relationship between liver metastasis and survival outcomes of patients receiving ICIs treatment. We searched four main databases, including PubMed, EMBASE, Cochrane Library, and Web of Science. Overall survival (OS) and progression-free survival (PFS) were the survival outcomes of our concern. Hazard ratio (HR) with 95% confidence interval (CI) were used to evaluate the relationship between liver metastasis and OS/ PFS. Finally, 163 articles were included in the study. The pooled results showed that patients with liver metastasis receiving ICIs treatment had worse OS (HR=1.82, 95%CI:1.59-2.08) and PFS (HR=1.68, 95%CI:1.49-1.89) than patients without liver metastasis. The effect of liver metastasis on ICIs efficacy differed in different tumor types, and patients with urinary system tumors (renal cell carcinoma OS: HR=2.47, 95%CI:1.76-3.45; urothelial carcinoma OS: HR=2.37, 95%CI:2.03-2.76) had the worst prognosis, followed by patients with melanoma (OS: HR=2.04, 95%CI:1.68-2.49) or non-small cell lung cancer (OS: HR=1.81, 95%CI:1.72-1.91). ICIs efficacy in digestive system tumors (colorectal cancer OS: HR=1.35, 95%CI:1.07-1.71; gastric cancer/ esophagogastric cancer OS: HR=1.17, 95%CI:0.90-1.52) was less affected, and peritoneal metastasis and the number of metastases have a greater clinical significance than liver metastasis based on univariate data. For cancer patients receiving ICIs treatment, the occurrence of liver metastasis is associated with poor prognosis. Different cancer types and metastatic sites may hold a different prognostic effect on the efficacy of ICIs treatment in cancer patients.