ESR1 and breast cancer: The dormancy and reactivation of long-established disseminated tumor cells (DTCs) in distant organs following primary tumor resection constitute a pivotal factor contributing to tumor recurrence and pose a significant challenge in antitumor therapy.136,252–254 Breast cancer continues to recur 5-20 years post-treatment, particularly in ER+ breast cancer cases.255,256 The implication is that the distal site DTCs have remained dormant for numerous years before the clinical detectability of the tumor.257