The combination of size‐based separation and selection‐free technology provides higher circulating tumor cells detection sensitivity than either method alone in patients with metastatic prostate cancer

OBJECTIVE: To investigate the CTC capture abilities of two technologies that are not dependent on cell-surface marker expression: a selection-free platform, the AccuCyte(R)-CyteFinder(R) system (Rarecyte) and a size-based platform, the fluid-assisted separation technology (FAST). In addition, the combination of the two systems to more completely assess CTCs was investigated. METHODS: 28 patients with metastatic prostate cancer were included. Two 6 ml peripheral blood samples were collected from each patient at the same timepoint. The samples were then subjected to the two different technology platforms in parallel. An additional group of samples was acquired by applying the waste chamber material from the FAST group tests (flow-through that goes through the FAST filter membrane) to the Rarecyte system for the detection any CTCs that were not captured by FAST. RESULTS: The three groups had significantly different putative CTC positive tests, with positive rates of 29% for Rarecyte, 57% for FAST and 79% for combination. We also assessed CTC phenotype. 56.6% of CTCs were CK+/EpCAM-, 3.1% were CK-/EpCAM+, and 40.3% were CK+/EPCAM+. Captured CTCs diameter ranged from 5.2-16. 9 microm. The mean CTC size from the FAST waste chamber was significantly smaller. The diameters for each of the phenotypic groups were significantly different. CONCLUSIONS: These data highlight disparities in the positive rates and enumerated CTC numbers detected by two techniques. Notably, the combination of two technologies resulted in the highest CTC capture rates. Smaller CTCs were more likely to be missed by the FAST system as they passed through the filter system. Sizes of CTCs varied with different cell surface marker phenotypes.