Prognostic value of pretreatment smoking status for small cell lung cancer: A meta-analysis

Although tobacco exposure remains the most important risk factor of tumorigenesis of small cell lung cancer (SCLC), its prognostic value has failed to reach a consensus until now. Accordingly, we conducted a meta-analysis to investigate the prognostic value of pretreatment smoking status (smokers vs. never-smokers) in SCLC.

The four databases PubMed, Medline, Embase, and Cochrane library were searched to identify the relevant literature from the inception dates to 24 June 2020. The primary outcome was overall survival (OS), and the secondary endpoint was progression-free survival (PFS). The hazard ratios (HRs) with 95% confidence intervals (CIs) were extracted to assess the relationship between pretreatment smoking status and patient survival. Sensitivity analysis was performed to assess the stability of the pooled results. Begg's funnel plot and Egger's test were applied to detect the publication bias. All statistical analyses were performed using RevMan V.5.3 and STATA version 15.0 software.

A total of 27 studies involving 12 047 patients with SCLC (9137 smokers and 2910 never-smokers) were included in this meta-analysis. The results showed that smoking history was closely related to poorer survival outcome (OS: HR = 1.17, 95% CI: 1.12-1.23, P < 0.00001; I² = 0%; PFS: HR = 1.20, 95% CI: 1.06-1.35, P = 0.004; I² = 0%).

Smoking history should be considered as an independent poor prognostic factor for patients with SCLC. More large-scale prospective studies are warranted to testify the prognostic value of pretreatment smoking status.