Sparano J, et al. - Researchers investigated the association of the presence of circulating tumor cells (CTCs) in a peripheral blood sample obtained approximately 5 years after diagnosis with late clinical recurrence of operable human epidermal growth factor receptor 2–negative breast cancer. In this per-protocol secondary analysis of a randomized clinical trial, 26 of 547 patients (4.8%) with localized breast cancer displayed circulating tumor cells 5 or more years after diagnosis; and these cells were associated with a higher risk of recurrence among patients with hormone receptor–positive breast cancer.