Symonds EL, Pedersen SK, Murray D, et al. - Considering that the chance of a cure may improve via sensitive detection of recurrent colorectal cancer (CRC) assessed by measuring circulating tumor DNA (ctDNA), researchers here compared a quantitative methylated ctDNA test with carcinoembryonic antigen (CEA) in the setting of surveillance for recurrence. ctDNA (methylated branched-chain amino acid transaminase 1 [BCAT1]/Ikaros family zinc-finger 1 protein [IKZF1]) and CEA were determined in the blood samples collected either during surveillance or within 12 months of the confirmation of recurrence. The analysis suggests a superior sensitivity of the quantitative ctDNA test in comparison with CEA without a difference in the specificity for identifying recurrent CRC. When adjustments were made for other predictors of the presence of recurrence, the independent predictive value of a positive ctDNA test but not of CEA was recognized.