The clinical and prognostic impact of aldehyde dehydrogenase 1 in non-small cell lung cancer: a meta-analysis

Background: Aldehyde dehydrogenase 1 (ALDH1) has been identified as a cancer stem cell marker. However, the clinical role of ALDH1 in non-small cell lung cancer (NSCLC) remains conflicting. This study was conducted to investigate the correlation of ALDH1 with NSCLC patients' clinicopathological characteristics and prognosis. Methods: The electronic databases were searched for the available literature. The pooled odds ratios (ORs) with 95% confidence intervals (CIs) or hazard ratios (HRs: multivariate Cox analysis) with 95% CIs were used to evaluate the impact of ALDH1 on NSCLC. Results: Final 13 eligible studies with 2,407 patients published between 2009 and 2019 were identified. ALDH1 expression was not correlated with age, gender, smoking behavior, clinical stage, histological grade, lymph node metastasis, and distal metastasis, but the results demonstrated a positive association of ALDH1 expression with recurrence (yes vs. no: OR =2.82, 95% CI, 1.17-6.80, P=0.021) and a negative association of ALDH1 expression with vascular invasion (positive vs. negative: OR =0.63, 95% CI, 0.41-0.98, P=0.04). ALDH1 expression was significantly lower in adenocarcinoma (AD) than in squamous cell carcinoma (SCC) (OR =0.39, 95% CI, 0.30-0.51, P<0.001). Multivariate Cox analysis showed that ALDH1 expression was not associated with overall survival (OS) and disease-free survival (DFS), but was correlated with improved disease-specific survival (DSS) (HR =0.47, 95% CI, 0.22-0.98, P=0.043). Conclusions: ALDH1 expression may be an independent favorable prognostic marker for DSS in NSCLC.