Comparative analysis of circulating tumor DNA stability In K3EDTA, Streck, and CellSave blood collection tubes

Abstract

Objectives Optimal conditions for blood collection for circulating tumor DNA (ctDNA) are still being developed. Although both Streck and EDTA tubes are commonly used, their ability to stabilize ctDNA as a function of time and temperature post-collection has not been thoroughly studied. Additionally, the potential utility of CellSave tubes (commonly used for circulating tumor cell) for ctDNA measurements has not been studied. Design and methods Blood was collected into Streck, EDTA, and CellSave tubes from ten patients with metastatic breast cancer enrolled in the MI-ONCOSEQ tumor sequencing program at the University of Michigan and kept either on ice or at room temperature until plasma isolation. Plasma was processed after 2, 6, and 48 h post-collection. We used droplet digital PCR (ddPCR) to quantify plasma ctDNA and wild-type DNA for six patients who had tumor tissue mutations represented in commercially available ddPCR assays. Results ctDNA abundance was similar and stable for up to 6 h in all tube types, and there was no effect of storage temperature on the yield for Streck and EDTA tubes. After 48 h, however, one out of four patients with detectable ctDNA showed a ~ 50% decline in ctDNA in the EDTA tube, and three out of six patients showed a 2–3-fold increase in wild-type DNA in the EDTA tube. Conclusions Streck, EDTA, and CellSave tubes showed similar performance in preserving ctDNA for up to 6 h before plasma isolation. Streck and CellSave tubes more consistently stabilized ctDNA and wild-type DNA at 48 h than EDTA tubes.