Clinical significance of carcinoembryonic antigen-, cytokeratin 19-, or survivin-positive circulating tumor cells in the peripheral blood of esophageal squamous cell carcinoma patients treated with radiotherapy

Circulating tumor cells (CTCs) have been associated with clinical outcome in various malignancies. The aim of this study was to examine CTC status in the peripheral blood of patients with esophageal squamous cell carcinoma (ESCC) before and after radiotherapy, and to evaluate its clinical significance. A total of 72 ESCC patients treated with radical radiotherapy were enrolled in this study. The nested reverse-transcriptase polymerase chain reaction was used to detect the three representative markers of CTCs, namely carcinoembryonic antigen, cytokeratin 19, and survivin. The results showed that CTC(+), a status with positive expression of at least one of these three markers, in patients with ESCC pre- and post-radiotherapy were 54.2% (39/72) and 38.9% (28/72), respectively (P= 0.059). Furthermore, CTC (+) in patients pre- or post-radiotherapy was both correlated with lymph metastasis and adverse 2-year progression-free survival. It was also found that changes in CTC status after radiotherapy could reflect patients' response to radiotherapy. The response rates in cases with CTC status pre-radiotherapy(+)/post-radiotherapy(+), pre-radiotherapy(-)/post-radiotherapy(+), pre-radiotherapy(-)/post-radiotherapy(-), pre-radiotherapy(+)/post-radiotherapy(-) were 58.3% (21/36), 0% (0/3), 73.7% (14/19), and 85.7% (12/14), respectively. In a multivariate analysis of Cox proportional hazard model, only CTC (+) post-radiotherapy was an independent unfavorable prognostic factor for ESCC apart from subsequent chemotherapy and patients' Karnofsky performance status scores. In conclusion, positive detection of CTCs in patients with ESCC after radiotherapy may be a promising biomarker for radiation efficiency and prognosis assessment in ESCC.