Comparison of two detection systems for circulating tumor cells among patients with renal cell carcinoma

Background/aims Detection of circulating tumor cells (CTCs) in cancer patients has diagnostic and prognostic importance. However, the clinical implications of CTC detection in patients with renal cell carcinoma (RCC) are still unclear. In this study, we investigated the clinical significance of CTCs using two detection systems, the CellSearch system (CSS) and isolation by size of epithelial tumor cells (ISET), among RCC patients. Methods We recruited 36 RCC patients and 22 healthy volunteers as controls. Blood was drawn before treatment. Samples were analyzed using the CSS and ISET. We prospectively followed the RCC patients to determine overall and progression-free survival. Results We did not detect CTCs in the control group using either the CSS or ISET. CTCs were detected in 7/36 patients (19.4%) using the CSS and in 13/36 patients (36.1%) using ISET, while circulating microemboli (CTMs) were detected in three patients (8.3%). The presence of ISET-detected CTCs correlated with clinical tumor node metastasis (TNM) stages, while the CSS-detected CTCs did not. After 36 months (median), CTCs detected by both methods failed to correlate with overall and progression-free survival among RCC patients. Conclusion We discovered that ISET is more suitable than the CSS for detecting CTCs in RCC patients. The presence of CTCs/CTMs in RCC patients correlated with higher TNM stages, suggesting that the presence of CTCs could be a prognostic marker in RCC patients.