Circulating tumor cells: A novel prognostic factor for newly diagnosed metastatic breast cancer

Purpose Metastatic breast cancer (MBC) is incurable; its treatment is palliative. We investigated whether the presence of circulating tumor cells (CTCs) predicts treatment efficacy, progression-free survival (PFS), and overall survival (OS) in patients with newly diagnosed MBC who were about to start first-line therapy. Patients and Methods One hundred seventy-seven patients with measurable MBC were enrolled onto a prospective study. Eighty-three of the 177 patients were entering first-line treatment, and these patients are the focus of this analysis. CTCs from 7.5 mL of whole blood drawn before treatment initiation (baseline) and monthly thereafter for up to 6 months were isolated and enumerated using immunomagnetics. Results The mean (+/- standard deviation) follow-up time was 11.1 +/- 4.4 months (median, 12.2 months). Forty-three patients (52%) had greater than or equal to five CTCs at baseline. The median PFS was 7.2 months (95% Cl, 4.9 to 9.4 months), and the median OS was more than 18 months. Patients with greater than or equal to five CTCs at baseline and at first follow-up (4 weeks) had a worse prognosis than patients with less than five CTCs (baseline: median PFS, 4.9 v 9.5 months, respectively; log-rank, P = .0014; median OS, 14.2 v > 18 months, respectively log-rank, P = .0048; first follow-up: median PFS, 2.1 v8.9 months, respectively;, log-rank, P = .0070; median OS, 11.1 v > 18 months, respectively; log-rank, P = .0029), CTCs before and after the initiation of therapy were strong, independent prognostic factors. Conclusion Detection of CTCs before initiation of first-line therapy in patients with MBC is highly predictive of PFS and OS. This technology can aid in appropriate patient stratification and design of tailored treatments. (C) 2005 by American Society of Clinical Oncology.