If you look hard enough.

The authors of this study looked really hard to detect circulating tumor DNA (ctDNA) in 45 patients prior to chemoradiation for locally-advanced esophageal cancer, with ctDNA comprising a median of only 0.7% of the patients’ total cell-free DNA. But it paid off. Detection of ctDNA after chemoradiation was associated with 18x the risk of tumor progression, 32x the risk of mets, and 23x the rate of recurrence or death. | Azad, Gastroenterology 2019