Prognostic significance of programmed cell death-ligand 1 expression on circulating tumor cells in lung cancers: systematic review and meta-analysis

Background: This meta-analysis aims to investigate the correlation between programmed cell death-ligand 1 (PD-L1) expression on circulating tumor cells (CTCs) and its prognostic significance. Methods The authors retrieved literature databases for eligible studies published before January 10, 2023. Hazard ratio (HR) with 95% confidence interval (CI) was used to assess the correlation between PD-L1 expression on CTCs and overall survival (OS) and progression-free survival (PFS). Results This study included 10 articles involving 731 patients. The pooled results showed that PD-L1 + CTCs were significantly associated with OS (HR = 1.87, 95% CI 1.02–3.44, P = 0.04) but not with PFS (HR = 1.19, 95% CI 0.77–1.82, p = 0.43). The subgroup analysis demonstrated that PD-L1 + CTCs were associated with worse PFS (HR = 1.19, 95% CI 0.77–1.82, P = 0.03) and OS(HR = 2.05, 95% CI 1.5–2.8, P༜0.01) for patients who received back-line immune checkpoint inhibitors (ICIs) treatment. No significant clinical significance was observed for PFS when considering CTCs enrichment and cutoff. In the immunologic enrichment group, PD-L1 + CTCs were associated with worse OS (HR = 2.48, 95% CI 1.43–4.29, P=0.001). Regarding the PD-L1 detection method and region, PD-L1 + CTCs were associated with worse PFS/OS in the IF and European groups. Conclusions The expression of PD-L1 on circulating tumor cells (CTCs) is a promising prognostic marker for lung cancer, particularly in patients who received back line ICIs treatment.