Impact of liver metastases status on survival outcomes of first-line immunotherapy in extensive stage small cell lung cancer: a systematic review and meta-analysis

Purpose: This study aims to assess the impact of liver metastases status on survival outcomes of first-line immunotherapy in extensive stage small cell lung cancer (ES-SCLC) patients. Materials and methods: Comprehensive searches were conducted in the Cochrane Library databases, Embase, PubMed, and abstracts from WCLC, ESMO, and ASCO from inception to December 2022. Randomized controlled trials reporting progression-free survival (PFS) and/or overall survival (OS) of first-line immunotherapy in ES-SCLC patients were included. Results: Six trials involving 3501 patients were analyzed, comprising 1350 patients with liver metastases and 2151 without. The quality of the included trials was consistently high. Pooled results revealed that immunotherapy plus chemotherapy did not significantly improve PFS (hazard ratio [HR] = 0.82, 95% confidence interval [CI]: 0.68-1.00, P = 0.05) and OS (HR = 0.89, 95% CI: 0.79-1.00, P = 0.05) in ES-SCLC patients with liver metastases compared to chemotherapy alone. However, immunotherapy plus chemotherapy improved PFS (HR = 0.66, 95% CI: 0.57-0.77, P < 0.01) and OS (HR = 0.74, 95% CI: 0.67-0.82, P < 0.01) in ES-SCLC patients without liver metastases compared to chemotherapy alone. Conclusions: First-line immunotherapy plus chemotherapy significantly improved PFS and OS in ES-SCLC patients without liver metastases compared to chemotherapy alone. However, patients with liver metastases did not experience comparable benefits.