Fig. 2: Origin of the variants detected by liquid biopsy test.

By comparing the results obtained by the liquid biopsy panel to those from the other genomic panels, the origin of most of the identified variants was clarified. 29.1% (25/86) of the variants have germline origin (blue), 38.4% (33/86) were derived from clonal haematopoiesis (red), and the remaining 32.6% (28/86) were considered real ctDNA variants, potentially derived from the tumour (yellow). Regarding those tumour ctDNA variants, 17 were present in the tissue biopsy (60.7% of ctDNA variants, 19.8% of total) and 11 were not (39.3% of ctDNA variants, 12.8% of total). Of those absent in the tissue biopsy, other 5 variants were assumed to derive from the tumour in the light of serial liquid biopsies results (17.9% of ctDNA variants, 5.8% of total) whereas the suspected tumour origin of the other 6 (21.4% of ctDNA variants, 7.0% of total) could not be ascertained.