Detection of circulating tumour cells before and following adjuvant chemotherapy and long-term prognosis of early breast cancer.

Background: The detection of circulating tumour cells (CTC) is prognostic for disease recurrence in early breast cancer (BC). This study aims to investigate whether this prognostic effect persists or varies over time.

Methods: The study population consisted of prospectively included stage I-III BC patients. The presence of CK19 mRNA-positive CTC in the peripheral blood was evaluated before and after adjuvant chemotherapy, using a real-time RT-PCR assay. Longitudinal samples were collected for a subset of patients.

Results: Baseline CTC data were available from 1220 patients, while 1132 had both pre- and post-therapy data. After a median follow-up of 134.1 months, CTC positivity at baseline was associated with shorter overall survival (OS; HR = 1.72, 95% CI 1.34-2.21, p < 0.001). For disease-free survival, an interaction with time (p = 0.045) was observed. CTC positivity predicted early (within 5 years; HR = 1.76, 95 CI 1.33-2.32, p < 0.001) but not late recurrence (HR = 1.10, 95% CI 0.79-1.53, p = 0.577). Following adjuvant chemotherapy, more patients converted from CTC-positive to CTC-negative than vice versa (p < 0.001). Ten-year OS was 68.6% for + /+ and 86.7% for -/- group (p < 0.001). CTC status at follow-up predicted disease recurrence.

Conclusion: CTC detection pre- and post-adjuvant chemotherapy is prognostic for early relapse, supporting investigations for novel adjuvant therapeutic approaches.