Mutant IDH1 ctDNA levels from 7 of these 9 patients was clearly reduced following surgery (average time when first sampled 92 days) (CS09‐192 days, CS10‐130 days, CS21‐3 days, CS24‐107 days, CS12‐139 days, CS13‐162 days & CS27‐2 days) although in patient (CS27), with a dedifferentiated CS, the ctDNA subsequently had risen significantly when measured at day 118 reflecting disease progression (local recurrence and metastatic disease) (Fig. 3). This evidence concerns the gene IDH1 and metastatic neoplasm.