Validation of increased sample stability using the AccuCyte®-CyteFinder® CTC Platform to improve logistics in global clinical trials

Shipping blood to a central processing lab inside a narrow window is what limits where a global circulating tumor cell trial can enrol; this AACR 2022 poster reports validation of a 5-day hold in the AccuCyte collection tube, a higher-capacity prep kit, and frozen slide banking out to the equivalent of 4 years.

Presented by RareCyte and University of Washington.

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• Blood held 5 days in the AccuCyte collection tube showed no significant loss of CTC recovery or epithelial signal against the same sample processed at 24-72 hours. Ten breast and prostate samples carrying more than 10 CTC per 7.5 mL ran at both timepoints: the mean difference in recovery (24-72 hours minus 120 hours) was -17.3%, i.e. the 5-day draws recovered more on average, with the 95% CI of the mean (-47.5, 12.8) crossing zero and the 95% limits of agreement (-100.0, 65.3) staying wide at this sample size. Two of the ten pairs did move on CK/EpCAM signal, and both were higher at 120 hours rather than lower.
• The higher-capacity AccuCyte prep kit gave CTC recovery equivalent to the version it replaces. New-kit-to-old-kit recovery ratios were read across 30 spiked tube pairs and 14 breast and prostate clinical pairs selected for 10+ CTC in at least one partner, with the median taken over all pairs. The flagged outliers show what that ratio is made of: 0.5 and 23.9 on the spikes, and a clinical 3.3 that is simply 10 CTC against 3.
• Slides banked at -20°C held through the equivalent of 4 years of storage, with estrogen receptor the exception. An accelerated-aging arm at 4°C modelled 4 years for the HER2/ER assay on BT474 cells and 5 years for the AR/SYP assay on 22Rv1 cells. Cell recovery, CK/EpCAM, CD45, HER2, SYP and AR each stayed above the lower limit of performance acceptability drawn on their panels; ER did not, which is why the poster's own results statement reaches only to most biomarkers tested.