Circulating tumor cells and bone metastases as detected by FDG-PET/CT in patients with metastatic breast cancer

Patients and methods: From May 2004 to January 2008, 195 patients with relapsed/progressive MBC underwent whole-body FDG-PET/CT and provided blood samples for assessment of CTC count. Results: Higher CTC numbers were detected in patients with bone metastases relative to those with no bone lesions (mean 65.7 versus 3.3, P = 0.0122) and in patients with multiple bone metastases relative to those with one or two bone lesions (mean 77.7 versus 2.6, P < 0.001). CTCs predicted overall survival (OS) in 108 patients with multiple sites of metastases including bone (P = 0.0008) but not in 58 without bone metastases (P = 0.4111) and in 29 with bone involvement only (P = 0.3552). All 15 patients but one with human epidermal growth factor receptor 2 (HER-2) positive tumors who were treated with trastuzumab-based regimens had < 5 CTCs at progression. In multivariate analysis, CTCs, but not bone metastases, remained a significant predictor of OS. Conclusion: Presence of extensive bone metastases as detected by FDG-PET/CT is associated with increased CTC numbers in MBC.