Organ-specific immune checkpoint inhibitor treatment in lung cancer: a systematic review and meta-analysis

OBJECTIVES: Based on the acknowledged organ-specific immune microenvironment, little is known regarding the efficacy of immunotherapy in patients with lung cancer according to metastatic sites. This meta-analysis aimed to explore the efficacy of immune checkpoint inhibitors (ICIs) vs chemotherapy in patients with lung cancer with liver metastases (LM) or brain metastases (BM). DESIGN: Meta-analysis and systematic review. DATA SOURCES: We systematically searched in electronic databases (PubMed, EMBASE, Cochrane Library and Web of Science), up to 31 January 2022. We also reviewed the abstracts from major international conferences. Eligibility criteria were randomised controlled phase II or III trials reporting the overall survival (OS) or progression-free survival (PFS) of LM or BM subsets. DATA EXTRACTION AND SYNTHESIS: Hazard ratios (HRs) with 95% CIs for OS and PFS were extracted and aggregated using a random-effects model. RESULTS: Twenty-four randomised controlled trials with available outcomes for patients with BMs or LMs were identified. A total of 1124 patients with BM and 2077 patients with LM were included in the analysis. The pooled OS HR of patients with LMs was 0.83 (95% CI 0.72 to 0.95), and that of patients without LM 0.73 (95% CI 0.69 to 0.79). LM was associated with less benefits from ICIs. In patients with BM treated with ICIs, the pooled OS HR compared with the control arms was 0.71 (95% CI 0.53 to 0.94). Subgroup analyses by histology suggested that only patients with non-small cell lung cancer (NSCLC) with BM could gain benefit from ICIs (HR 0.53, 95% CI 0.41 to 0.68). BM negatively influenced efficacy of immunotherapy in patients with small cell lung cancer. CONCLUSIONS: Our results showed immunotherapy demonstrated efficacy in patients with lung cancer with LM and BM, survival benefits dominantly favoured patients with NSCLC. Patients with lung cancer with LM obtained less benefits from ICIs than those without. Therefore, organ-specific immunotherapeutic approaches should be considered. PROSPERO REGISTRATION NUMBER: CRD42020212797.