Clinical significance of detecting circulating tumor cells in patients with esophageal squamous cell carcinoma by EpCAM-independent enrichment and immunostaining-fluorescence in situ hybridization

Circulating tumor cells (CTCs) are tumor cells present in the bloodstream, which originate from tumor sites, and are ultimately responsible for metastasis or relapse in several types of cancer. However, to the best of our knowledge, only a few studies have investigated these extremely rare cells in esophageal squamous cell carcinoma (ESCC). In the present study, 63 patients with ESCC and 50 healthy donors were recruited, and the potential clinical significance of CTCs was assessed using subtraction enrichment and immunostaining-fluorescence in situ hybridization. Blood samples were collected at the following times: At first diagnosis, following neoadjuvant chemoradiotherapy, 24 h and 13 days post-surgery, and every 3 months during follow-up. Cytokeratin (CK)-positive and clustered CTCs only accounted for 1% of total CTCs detected, whereas most CTCs were CK-negative aneuploid cells. Patients with ESCC (n=63) had higher CTC counts compared with healthy donors (control group; n=50) (area under curve=0.807, median CTC count, 2 vs. 0). However, there was no statistical association between CTC counts and sex, age, pathological stage, tumor location, tumor depth or lymph node involvement (P>0.05). The association of tumor development with CTC status and other circulating biomarkers was monitored in patients for a further 2 years. The results revealed that a change in CTC counts between first diagnosis and 13 days post-surgery (ΔCTC) of ≥2/7.5 ml peripheral blood could be applied for predicting progression-free survival (hazard ratio, 3.922; 95% confidence interval, 0.907–16.951; P<0.05) in patients with ESCC. In conclusion, ΔCTC evaluation may be a promising indicator for predicting tumor prognosis and the clinical efficacy of treatment in patients with ESCC.