In the Brief Report titled “Assessment of Molecular Relapse Detection in Early-Stage Breast Cancer,”1 published online August 1, 2019, and in print on October 10, 2019, there were a data errors in the Results section. Validated personalized digital polymerase chain reaction assays were developed for 150 mutations (90.9%), not 91.5%. Of the 29 patients who relapsed, 23 (79.3%), not 88.4%, relapsed with prior circulating tumor DNA detection, whereas 6 (20.7%), not 21.6%, relapsed without circulating tumor DNA detection before or at the time of relapse. This article has been corrected online.