Clinicopathological and prognostic value of circulating tumor cells in esophageal carcinoma: a meta-analysis

The associations between circulating tumor cells (CTCs) in peripheral blood and prognosis of patients with esophageal carcinoma (EC) have been investigated by a number of studies, but the results are not consistent. Therefore, this study aimed to explore this controversial subject. A literature database search was performed according to preferred reporting items for systematic reviews and meta-analyses (PRISMA) statement. The risk ratio (RR), hazard ratio (HR) and their 95% confidence intervals (CIs) were retained as the effect measures. If necessary, subgroup analyses and meta-regression should also be performed to clarify the heterogeneity. Thirty-three studies, containing 3,236 patients with EC, were included in this meta-analysis. The results showed that overall survival (OS) (HR = 2.14; 95% CI, 1.73-2.65) and progressionfree survival (PFS) (HR =2.29; 95% CI, 1.69-3.11) were worse in CTCs-positive patients. CTC positivity is also significantly associated with depth of infiltration (RR =1.42; 95% CI, 1.10-1.82, P=0.21) and tumor-node-metastasis (TNM) stage (RR =1.36; 95% CI, 1.09-1.69, P=0.22). However, there was no significant relationship between CTC-positive and distant metastasis (RR =1.58; 95% CI, 1.00-2.50, P=0.65). Detection of CTCs had prognostic value for EC patients. Positive CTC is associated with poor prognosis and some prognostic factors, such as depth of infiltration and TNM stage, but not related to metastasis.