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

Abstract

10554 Background: To investigate the effect of adjuvant taxane-free and taxane-based chemotherapy regimens on the elimination of circulating tumor cells (CTCs) in patients with early breast cancer. Methods: The presence of CK-19 mRNA-positive CTCs in the peripheral blood was evaluated both before and after chemotherapy, using a real-time RT-PCR assay, in 545 women with stage I-III breast cancer who received adjuvant taxane-free (FE75C and E75C) or taxane-based (sequential docetaxel followed by epirubicin/cyclophosphamide or docetaxel/epirubicin) chemotherapy. Results: Taxane-based regimens were more effective than taxane-free regimens in the elimination of CTCs since 49.7% and 33.0% of patients with detectable CTCs before chemotherapy, respectively, became CK19 mRNA-negative after completion of chemotherapy (p=0.015). The incidence of clinical relapses was higher in patients treated with taxane-free than in those treated with taxane-based (33.2% and 16.6%, respectively, p=0.00001). Patients treated with a taxane-free regimen had a significantly lower DFS compared to patients treated with a taxane-based chemotherapy (p=0.035); this difference was observed in patients with but not without detectable CTCs before chemotherapy (p=0.018 and p=0.481, respectively). Multivariate analysis revealed that the chemotherapy regimen was significantly associated with a prolonged DFS (HR: 2.00; 95% CI: 1.20-3.34) in patients with detectable CTCs. Conclusions: Elimination of CK-19 mRNA-positive CTCs during adjuvant chemotherapy may be an indicator of the efficacy of the chemotherapy regimen and this is associated with a favorable clinical outcome in patients with detectable CTCs