IDH1 and central nervous system cancer: While some tumor types such as colorectal cancer had high detection rates of ctDNA, less than 10% of patients with gliomas were detectable, the lowest detection rate across all 14 cancer types.13 While the study included 13 patients with an IDH1 mutant tumor, assessment of the plasma-derived cfDNA from all 13 patients did not reveal the presence of the mutation in the bloodstream.