41P Circulating Tumor Cells (CTCs) and Metronomic Oral Vinorelbine (OV) in Advanced Breast Cancer (ABC) Patients (PTS): Exploratory Prospective Analysis

Abstract

ABSTRACT Background CTC changes during treatment are an independent predictor of outcome in ABC pts. No data have been published concerning CTCs and metronomic chemotherapy. We postulate that anti-angiogenic property of metronomic chemotherapy, through its effect on the vessels endothelium, might drop off CTC count under therapy. We investigated whether metronomic oV may influence CTC count and hence limit the predictive role of CTCs in ABC pts. Patients and methods From February 2008 to June 2011, 56 pts were treated with oV administered at 50 mg three times a week in a phase II study. We collected blood samples to assess CTC count at baseline and after the first re-evaluation of treatment. CTCs were enumerated using the CellSearch System. Correlation with clinical response was also performed. The Chi-square test was used to evaluate the association between the number of CTCs and patients' characteristics. Paired T-test and Mc Nemar test were used to evaluate changes in number of CTCs between time-points. Results CTC behaviour from baseline to first assessment allowed us to distinguish two groups: 0-4 CTCs and > 5 CTCs/7.5 ml of blood. At baseline, CTC level was associated with age (p = 0.02), 40 (71.5%) pts had 5 and with PR or stable disease did not show CTC changes (p = 0.65) from baseline. A borderline significant difference was observed for PD (p = 0.06) that occurred in 7 (63.6%) pts with persistent CTC > 5, and in 8 (80%) pts with CTCs shifting from 0-4 to > 5. Conclusion To our knowledge, this is the first analysis of CTC behaviour during metronomic chemotherapy. Variations in CTC level do not appear to be affected by continuous low-dose administration of oV. However, high-powered prospective designs are needed to clarify the meaning of CTC count over time, in order to improve response to treatment and monitoring therapy. Disclosure All authors have declared no conflicts of interest.