ctDNA Analysis General Clinical Lab

Circulating tumor DNA (ctDNA) involves the analysis of DNA fragments derived from a tumor. These are DNA fragments that, outside cells, are "freely" present in the blood plasma. ctDNA can be detected in different tumor types, with detection varying by tumor type and depending on stage of the disease [1]. Much is now known about the role of ctDNA in diagnostics. As a predictive marker, ctDNA can be used when tissue collection is not possible or no adequate tumor material has been obtained for analysis. For lung cancer, this has been brought together in the cieBOD advice "ctDNA in blood plasma as a predictive analysis in lung cancer".

Three aspects for the use of ctDNA are important: on the one hand, the concordance between blood and tissue. A large number of publications show that ctDNA is found in 70-80% of patients with the same mutations compared to tissue. In the remaining 20-30%, only ctDNA may be positive or only the tissue. A second aspect is the sensitivity of the analysis. The amount of ctDNA in the blood correlates with the tumor volume and thus with the probability of detecting ctDNA in the background of cfDNA. A third aspect is the impact of the source (ctDNA or tissue) in which a mutation is found on the outcomes of treatment. Here too, a constant picture emerges in the literature: for the outcomes (PFS, RFS, OS, ORR) it does not matter whether the treated mutation is found in blood or in tissue.

ctDNA can be used for multiple applications in addition to predictive analysis, for example the analysis for minimal residual disease after surgery, or longitudinal follow-up of patients on blood. These applications are currently not available in the Netherlands and can therefore not be offered within cancer diagnostics.

For the analysis of ctDNA, the Netherlands Cancer Institute uses droplet digital PCR (ddPCR) and Next Generation Sequencing (NGS). Where ddPCR looks at individual mutations, NGS looks broadly at multiple genes, fusions and copy number variations. In the case of primary screening for treatable mutations, we often opt for NGS (17 genes), in the case of a resistance question, we use a broader NGS panel (78 genes). ddPCR is still used in case of very specific questions or when a result is needed in the very short term

The shelf life of ctDNA is particularly affected by the increase in background DNA (derived from white blood cells) when stored for more than 6 hours at room temperature. If direct processing is not possible, STRECK pipes must be used. These tubes stabilize the cells for up to 5 days. This allows for direct shipment as thoroughbred via regular mail.

You can use the link to the application form at the top of this page to request an application package with a STRECK pipe. We will send you 2 STRECK tubes to the address you have provided as standard. Ensure proper identification of the tubes and form.

The results will be reported to you within 10 working days. On the application form you must state the email address at which you want to receive the results. Samples received before Tuesday are deployed the same week, with reporting on Thursday the following week.

You will receive the results via the email address you provided.  If mutations are found, an NGS analysis indicates whether they are activating. If no mutations are detected, this never completely excludes the presence of treatable mutations. Sensitivity of the analysis depends, for example, on the tumor volume, the concentration of ctDNA in blood and the amount of blood analyzed. In such cases, it is worth considering repeating the analysis after some time, in case of a larger tumor volume. 

For the performance of ctDNA analysis, we use the standard pathology declaration codes for molecular analysis.