Fig. 2

A Circulating-tumor DNA (ctDNA) was detected 6 months prior to the borderline elevation of cerebrospinal fluid (CSF) β-hCG in a patient (GCT011) with pituitary stalk thickening and presumed germinoma, offering the potential for early non-invasive diagnostics. B Liquid biopsy finding mirrors clinical course in a patient (GCT009) with bifocal germinoma where serial CSF samples were available. Presence of ctDNA in CSF sample collected after completion of chemotherapy (middle panel) suggested residual active disease in spite of equivocal enhancing signal from resolving ventricular disease on imaging (yellow arrow heads). C Liquid biopsy detected residual disease and clarified ambiguous radiologic findings after 2 cycles of chemotherapy in a patient with relapsed germinoma (GCT014). With the resolution of ventricular disease (yellow arrowhead) and hemorrhaging temporal lobe lesion (asterisk), repeat liquid biopsy on therapy indicated persistence of molecular disease at both copy-number and mutational (KRAS) levels (middle panel). The third CSF collected after completion of chemotherapy, including high-dose chemotherapy, and resection of the left temporal lesion showed no measurable residual disease