Differential effect of adjuvant taxane-based and taxane-free chemotherapy regimens the CK-19 mRNA-positive circulating tumour cells in patients with early breast cancer

Background: To determine the effect of adjuvant taxane-free and taxane-based chemotherapy regimens on the elimination of circulating tumour cells (CTCs) in patients with early breast cancer. Methods: The presence of CK-19 mRNA-positive CTCs in the peripheral blood was evaluated before and after chemotherapy, using a real-time RT-PCR assay, in a historical comparison of two cohorts of women with stage I-Ill breast cancer treated with adjuvant taxane-free (N = 211; FE75C or E75C) and taxane-based (N = 334; T/E75C or T/E-75) chemotherapy. Results: Taxane-based chemotherapy resulted in a higher incidence of CTCs' elimination than taxane-free regimens since 49.7% (74 of 149) and 33.0% (29 of 88) of patients with detectable CTCs before chemotherapy, respectively, turned negative post-chemotherapy (P = 0.015). Patients treated with taxane-free regimens had a significantly lower disease-free survival (DFS) (P = 0.035) than patients treated with taxane-based regimens; this difference was observed in patients with but not without detectable CTCs before chemotherapy (P = 0.018 and P = 0.481, respectively). The incidence of deaths was significantly higher in the taxane-free cohort of patients with but not without detectable CTCs before chemotherapy compared with that of the taxane-based cohort (P = 0.002). Multivariate analysis revealed that the chemotherapy regimen was significantly associated with prolonged DFS (HR: 2.00; 95% CI = 1.20-3.34). Conclusion: Elimination of CK-19 mRNA-positive CTCs during adjuvant chemotherapy seems to be an efficacy indicator of treatment and is associated with a favourable clinical outcome of patients with detectable CTCs before chemotherapy.