Clinical significance of tumor cells in the peripheral blood of patients with esophageal squamous cell carcinoma

Circulating tumor cells (CTCs) are suspected of predicting the prognosis of malignant tumor, but there are few relevant reports specific to esophageal squamous cell carcinoma (ESCC). This study investigated the clinical significance of CTCs in patients with ESCC. Sixty patients with ESCC were enrolled, from whom CTCs had been tested by our team previously. Peripheral blood samples were obtained from these patients before treatment; and CTCs were assayed by isolation by size of epithelial tumor cells (ISET). Associations between the presence of CTCs and patients’ clinicopathological parameters and clinical outcomes were analyzed. CTCs were detected in 20 patients (33.3%), who experienced significantly shorter progression-free survival (PFS) than did the CTC-negative patients. Overall, PFS was negatively associated with the number of CTCs. Multivariate analyses showed that a CTC count >2 was a strong independent prognostic indicator of tumor recurrence (hazard ratio [HR] 5.63; 95% confidence interval [CI] 1.77–17.89; P = .003). In the subgroup of 50 patients who underwent R0 resection and postoperative adjuvant radiotherapy or chemotherapy, CTC was a strong, independent, and prognostic indicator of tumor recurrence (HR 10.70; 95% CI, 1.40–81.91; P = .022). The number of CTCs correlated with the T stage (r = 0.26, P = .043) but not with the N or M stage. For subgroups in stages II or I-IIIB or T3 or T3 + T4, the PFS of patients with CTCs > 1 or > 2 was significantly shorter than that of the patients with CTCs ≤ 1 or CTCs ≤ 2. In the stage III or T3 + T4 groups, the PFS of patients with CTCs > 0 was significantly shorter than that of patients with CTC = 0. This is the first study to report that the CTC detected by ISET is an independent and prognostic indicator of patients’ outcome in ESCC. Consideration of CTCs may improve the accuracy of preoperative staging in ESCC.