Survival benefit of immune checkpoint inhibitors according to the histology in non-small-cell lung cancer: A meta-analysis and review

Immune checkpoint inhibitors (ICIs) have been approved for patients with advanced non-small-cell lung cancer (NSCLC), regardless of histology. However, histologic subtypes of NSCLC may influence treatment outcomes of ICIs. We conducted this meta-analysis to investigate if there is difference in survival benefits of ICIs between squamous (SQ) and non-squamous (non-SQ) NSCLC. We searched PubMed, MEDLINE, EMBASE and ESMO databases. We included randomized controlled trials with the data of survival outcomes in advanced NSCLC patients treated with ICIs. From 7 eligible studies, 998 patients with SQ NSCLC and 2,769 with non-SQ NSCLC were included in the meta-analysis. ICIs improved progression-free survival (PFS) significantly in patients with SQ NSCLC (HR = 0.68 [95% confidence interval (CI), 0.51-0.91], P = 0.01), compared to chemotherapy. For patients with non-SQ NSCLC, however, ICIs were not associated with significant improvement of PFS (HR = 0.88 [95% CI, 0.67-1.16], P = 0.37). In terms of overall survival (OS), ICIs prolonged OS significantly in both SQ (HR = 0.71 [95% CI, 0.60-0.83], P < 0.0001) and non-SQ NSCLC (HR = 0.77 [95% CI, 0.63-0.94], P = 0.01). In conclusion, this meta-analysis indicates that ICIs significantly prolong OS in both SQ and non-SQ NSCLC.