Prognostic value of circulating tumor cells detected with the CellSearch system in esophageal cancer patients: a systematic review and meta-analysis

Background: Esophageal carcinoma (EC) is the seventh-most prevalent tumor in the world, which is still one of the primary causes of tumor-related death. Identifying noteworthy biomarkers for EC is particularly significant in guiding effective treatment. Recently, circulating tumor cells (CTCs) in peripheral blood (PB) were intensively discussed as prognostic markers in patients with EC. However, an ongoing controversy still exists regarding the prognostic significance of CTCs determined by the CellSearch system in EC sufferers. This meta-analysis was designed to approach this topic. Methods: We systematically conducted searches using PubMed, Medline, Web of Science and the Cochrane Library for relevant studies, which were published through February 20, 2020. Using the random-effects model, our study was performed in Review Manager software, with odds ratios (ORs), risk ratios (RRs), hazard ratios (HRs) and 95% confidence intervals (CIs) as the effect values. Results: Totally 7 articles were finally included in this study. For clinicopathological characteristics, the pooled results on TNM stage indicated that the III/IV group had higher rate of CTCs compared with the I/II group (OR = 1.36, 95% CI: 0.68-2.71, I-2 = 0%). Incidence of CTCs was higher in patients with T3/T4 stage (OR = 2.92, 95% CI: 1.31-6.51, I-2 = 0%) and distant metastasis group (OR = 5.18, 95% CI: 2.38-11.25, I-2 = 0%) compared to patients with T1/T2 stage or nonmetastatic group. The pooled analysis revealed that CTC positivity detected in EC patients was correlated with poor overall survival (OS) (HR = 2.83, 95% CI:1.99-4.03, I-2 = 0%) and relapse-free survival (RFS) (HR = 4.71, 95% CI:2.73-8.13, I-2 = 0%). When pooling the estimated RR, a poor therapeutic response to chemoradiotherapy was discovered in patients with CTC positivity (RR = 1.99, 95% CI:1.73-2.29, I-2 = 60%). Conclusions: In summary, our meta-analysis demonstrated that CTCs positivity determined by the CellSearch system are correlated with the prognosis of EC patients and might indicate a poor therapeutic response to chemotherapy in EC patients.