Monitoring the Response of Circulating Epithelial Tumor Cells to Adjuvant Chemotherapy in Breast Cancer Allows Detection of Patients at Risk of Early Relapse

Purpose To demonstrate that it is possible to monitor the response to adjuvant therapy by repeated analysis of circulating epithelial tumor cells (CETCs) and to detect patients early who are at risk of relapse. Patients and Methods In 91 nonmetastatic primary breast cancer patients, CETCs were quantified using laser scanning cytometry of anti–epithelial cell adhesion molecule–stained epithelial cells from whole unseparated blood before and during adjuvant chemotherapy. Results Numbers of CETCs were analyzed before therapy, before each new cycle, and at the end of chemotherapy. The following three typical patterns of response were observed: (1) decrease in cell numbers (> 10-fold); (2) marginal changes in cell numbers ( 10-fold) in numbers of CETCs. Twenty relapses (22%) were observed within the accrual time of 40 months, including one of 28 patients from response group 1, five of 30 patients from re...