Clinical Implications of Circulating Tumor Cells in Patients with Esophageal Squamous Cell Carcinoma: Cancer-Draining Blood Versus Peripheral Blood

Simple Summary: The levels of circulating tumor cells (CTCs) in blood from cancer-draining veins hold diagnostic and prognostic significance across various cancers. However, the research on esophageal squamous cell carcinoma (ESCC) remains limited. This study aimed to compare CTCs based on the sampling site (peripheral vein vs. cancer-draining azygos vein) and to investigate their association with the clinicopathological characteristics of patients with ESCC. The counts of CTCs and TWIST (+) CTCs were notably higher in blood from the azygos vein compared to that from the peripheral vein. However, CTCs and TWIST (+) CTCs in both peripheral and azygos vein blood did not show any correlation with clinicopathological characteristics. This study highlights the need for further research on the potential role of CTCs in azygos vein blood as predictive biomarkers for prognosis and chemotherapy responses in patients with ESCC. Circulating tumor cells (CTCs) in cancer-draining veins have diagnostic and prognostic value. However, studies on esophageal squamous cell carcinoma (ESCC) are limited. This study aimed to compare CTCs obtained from different sampling sites (peripheral vein vs. cancer-draining azygos vein) and to investigate their association with the clinicopathological characteristics of ESCC patients. Blood samples were collected preoperatively from both veins in 40 ESCC patients at Pusan National University Hospital from June 2020 to April 2022. CTCs were detected using a centrifugal microfluidic method with fluid-assisted separation. CTCs and TWIST (+) CTCs were detected more frequently in the azygos vein blood than in the peripheral vein blood; however, the difference was not statistically significant (85.0% [34/40] vs. 77.5% [31/40], p = 0.250 and 82.5% [33/40] vs. 75.0% [30/40], p = 0.586, respectively). CTC and TWIST (+) CTC counts were significantly higher in the azygos vein blood than in the peripheral vein blood (7 vs. 3, p < 0.001, and 6 vs. 2, p < 0.001, respectively). CTCs and TWIST (+) CTCs from peripheral and azygos veins showed no association with clinicopathological characteristics. Further large-scale studies are needed to clarify their role as predictive biomarkers for prognosis and chemotherapy responses in ESCC patients.