Clinical utility of circulating tumour cell-based monitoring of late-line chemotherapy for metastatic breast cancer: the randomised CirCe01 trial.

<bold>Background: </bold>CirCe01 trial aimed to assess the clinical utility of circulating tumour cell (CTC)-based monitoring in metastatic breast cancer (MBC) patients beyond the third line of chemotherapy (LC).<bold>Methods: </bold>CirCe01 was a prospective, multicentre, randomised trial (NCT01349842) that included patients with MBC after two systemic LC. Patients with ≥5 CTC/7.5 mL (CellSearch®) were randomised between the CTC-driven and the standard arm. In the CTC arm, changes in CTC count were assessed at the first cycle of each LC; patients in whom CTC levels predicted early tumour progression had to switch to a subsequent LC.<bold>Results: </bold>Greater than or equal to 5 CTC/7.5 mL were observed in N = 101/204 patients. In the CTC arm (N = 51), 43 (83%) and 18 (44%) patients completed CTC monitoring in the third and fourth lines, respectively, and 18 (42%) and 11 (61%) of these patients, respectively, had no CTC response. Thirteen (72%) and 5 (46%) of these patients underwent early switch to the next LC. Overall survival was not different between the two arms (hazard ratio = 0.95, 95% confidence interval = [0.6;1.4], p = 0.8). In subgroup analyses, patients with no CTC response who switched chemotherapy experienced longer survival than patients who did not.<bold>Conclusions: </bold>Due to the limited accrual and compliance, this trial failed to demonstrate the clinical utility of CTC monitoring.<bold>Clinical Trial Registration: </bold>NCT, NCT01349842, https://clinicaltrials.gov/ct2/show/NCT01349842 , registered 9 May 2011. [ABSTRACT FROM AUTHOR]