The use of liquid biopsies, tests that look for variants in cell-free DNA (cfDNA) shed by tumors into blood plasma, could lead to misdiagnosis and inappropriate treatment in many cancers, according to University of Washington researchers. The tests misidentified a noncancer mutation that is particularly common in older people as a mutation used as a biomarker for PARP inhibitors indicated for use in prostate cancer, a study published in JAMA Oncology found, but the problem likely extends to other malignancies.