ObjectivesMaking liquid biopsy testing widely available requires a concept to ship whole blood at ambient temperatures while retaining the integrity of the cell-free DNA (cfDNA) population and stability of blood cells to prevent dilution of circulating tumor DNA (ctDNA) with wild-type genomic DNA. The cell- and DNA-stabilizing properties of Streck Cell-Free DNA BCT blood collection tubes (cfDNA BCTs) were evaluated to determine if they can be utilized in combination with highly sensitive mutation detection technologies.MethodsVenous blood from healthy donors or patients with advanced colorectal cancer (CRC) was collected in cfDNA BCTs and standard K2EDTA tubes. Tubes were stored at different temperatures for various times before plasma preparation and DNA extraction. The isolated cfDNA was analyzed for overall DNA yield of short and long DNA fragments using qPCR as well as for mutational changes using BEAMing and Plasma Safe-Sequencing (Safe-SeqS).ResultsCollection of whole blood from healthy individuals in cfDNA BCTs and storage for up to 5 days at room temperature did not affect the DNA yield and mutation background levels (n = 60). Low-frequency mutant DNA spiked into normal blood samples as well as mutant circulating tumor DNA in blood samples from CRC patients collected in cfDNA BCTs were reliably detected after 3 days of storage at room temperature. However, blood samples stored at ≤ 10°C and at 40°C for an extended period of time showed elevated normal genomic DNA levels and an abnormally large cellular plasma interface as well as lower plasma volumes.ConclusionWhole blood shipped in cfDNA BCTs over several days can be used for downstream liquid biopsy testing using BEAMing and Safe-SeqS. Since the shipping temperature is a critical factor, special care has to be taken to maintain a defined room temperature range to obtain reliable mutation testing results.

Excellent pre-analytical stability is an essential precondition for reliable molecular profiling of circulating tumor DNA (ctDNA) in oncological diagnostics. Therefore, in vitro degradation of ctDNA and the additional release of contaminating genomic DNA from lysed blood cells must be prevented. Streck Cell-Free DNA blood collection tubes (cfDNA BCTs) have proposed advantages over standard K2EDTA tubes, but mainly have been tested in healthy individuals. Blood was collected from cancer patients (n = 53) suffering from colorectal (n = 21), pancreatic (n = 11), and non-small-cell lung cancer (n = 21) using cfDNA BCT tubes and K2EDTA tubes that were processed immediately or after 3 days (BCTs) or 6 hours (K2EDTA) at room temperature. The cfDNA isolated from these samples was characterized in terms of yield using LINE-1 qPCR; the level of gDNA contamination; and the mutation status of KRAS, NRAS, and EGFR genes using BEAMing ddPCR. CfDNA yield and gDNA levels were comparable in both tube types and were not affected by prolonged storage of blood samples for at least 3 days in cfDNA BCTs or 6 hours in K2EDTA tubes. In addition, biospecimens collected in K2EDTA tubes and cfDNA BCTs stored for up to 3 days demonstrated highly comparable levels of mutational load across all respective cancer patient cohorts and a wide range of concentrations. Our data support the applicability of clinical oncology specimens collected and stored in cfDNA BCTs for up to 3 days for reliable cfDNA and mutation analyses.

Liquid profiling based on circulating tumor DNA (ctDNA) extracted from blood has become a powerful diagnostic approach in oncology. Making ctDNA analysis broadly available requires shipping whole blood to a clinical laboratory while ensuring cell-free DNA (cfDNA) and blood cell integrity to prevent dilution of ctDNA with cellular genomic DNA. Since standard EDTA blood collection tubes cannot retain this integrity for a prolonged time, several laboratories have proposed Streck Cell-Free DNA blood collection tubes (Streck cfDNA BCTs) as an alternative for sample collection. Qualification data for the use of Streck cfDNA BCTs in oncology is limited and mainly based on blood collected from healthy individuals as well as data extrapolated from the prenatal field. However, the data generated from these samples may not represent the unique dynamics of clinical oncology specimens and therefore a study of true clinical oncology samples is required to support the use of Streck cfDNA BCT tubes in routine practice. In this study, we performed a clinical evaluation of cfDNA sample integrity from matched Streck cfDNA BCTs vs standard EDTA tubes from colorectal, pancreatic and non-small cell lung cancer patients (N > 50). Blood drawn into Streck cfDNA BCTs was either processed immediately or 3 days after phlebotomy. DNA quantification was followed by BEAMing digital PCR (OncoBEAM™) on KRAS, NRAS and EGFR mutations and compared to matching specimens collected in EDTA tubes. Our results suggest that cfDNA yield as well as the genomic DNA background is not affected by prolonged storage of clinical samples in Streck cfDNA BCTs for up to 3 days. In all sample sets containing mutated ctDNA, the detected mutational load was comparable between Streck cfDNA BCTs and EDTA tubes. In conclusion, this study represents a comprehensive clinical evaluation of Streck cfDNA BCTs vs EDTA tubes for ctDNA profiling. In conjunction with the findings of our previously presented Streck cfDNA BCT shipping condition studies, our data supports the compatibility of clinical oncology specimens collected in Streck cfDNA BCTs with the BEAMing technology. Citation Format: Inga Medina Diaz, Stefan Holdenrieder, Annette Nocon, Makbule Kobilay, Dirk Skowasch, Stefanie Held, Johanna Weiland, Claudia Stamm, Frank Diehl, Frank Holtrup. Clinical evaluation of streck cell-free DNA blood collection tubes for liquid profiling in oncology. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3145.