An early stage trial of an ultra-sensitive "liquid biopsy" that scans blood samples for traces of cancer DNA showed it was able to pick up at least one cancer mutation in most of the patients with advanced cancers that were studied. The findings, presented on Saturday at the American Society of Clinical Oncology meeting in Chicago, show the new test by Grail, a spinoff of gene sequencing company Illumina Inc, can identify bits of cancer DNA in the blood of patients already known to have cancer.