Better detection of circulating tumor DNA

A new method, fragment size analysis, has helped to more precisely detect circulating tumor DNA in blood samples.

Tumor cells leak some of their DNA molecules (circulating tumor DNA – ctDNA) to the bloodstream. Those sequences can be detected and tested for cancer-specific mutations, guiding treatment strategies or even support the screening process.

Detection of ctDNA is complicated because of interference with healthy cells’ DNA. Level of ctDNA is sufficient for cancer genome sequencing only in advanced-stage patients. Therefore the current use of ctDNA is limited to targeted approaches (e.g. looking for mutations in specific fragments of specific genes).

A new study used biological properties of ctDNA to leverage the coverage of sequencing. Most of the ctDNA molecules are shorter than 167 base pairs, and this threshold was used for selection. The method was called fragment size analysis and successfully enhanced the accuracy of mutation detection.

Fragment size analysis of ctDNA was tested in 344 samples of 200 patients with 18 cancer types.

More: “Enhanced detection of circulating tumor DNA by fragment size analysis”, F. Mouliere et al., 2018, doi:10.1126/scitranslmed.aat4921.