Circulating tumour cells are associated with increased risk of venous thromboembolism in metastatic breast cancer patients

BACKGROUND: Cancer is a risk factor for venous thromboembolism (VTE). Circulating tumour cells (CTCs) are an independent predictor of survival in metastatic breast cancer (MBC) patients. The aim of this study was to test the hypothesis that CTCs are associated with the risk of VTE in MBC patients. METHODS: This retrospective study included 290 MBC patients treated in the MD Anderson Cancer Center from January 2004 to December 2007. Circulating tumour cells were detected and enumerated using the CellSearch system before starting new lines of therapy. RESULTS: At a median follow-up of 12.5 months, 25 patients experienced VTE and 53 patients died without experiencing thrombosis. Cumulative incidence of thrombosis at 12 months was 8.5% (95% confidence interval (CI)=5.5%, 12.4%). Patients with CTCs ⩾1 and ⩾5 had a higher incidence of VTE compared with patients with 0 and <5 CTCs (12-month estimate, 11.7 and 11.6% vs 3 and 6.6%; P=0.006 and P=0.076, respectively). In the multivariate model, patients with CTCs⩾1 had a hazard ratio of VTE of 5.29 (95% CI=1.58, 17.7, P=0.007) compared with patients with no CTCs. CONCLUSION: These results suggest that CTCs in MBC patients are associated with increased risk of VTE. These patients should be followed up more closely for the risk of VTE.