Background: Circulating tumor cells (CTCs) and [18F]fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) are two promising new tools for monitoring therapy in patients with metastatic breast cancer. The two modalities showed high sensitivity in detection of bone relapse/progression from breast cancer (De Giorgi U et al. Ann Oncol 2009). In this study, we sought to evaluate the prognostic significance of two different modalities represented by the detection of CTC and FDG-PET/CT in patients with bone metastases from breast cancer treated with standard therapies. Our objective was to compare the two modalities to identify which technology could be more sensitive in prospectively monitoring such patients.Patients and Methods: This is a retrospective study of 54 patients with bone metastases from breast cancer without visceral metastases treated at The University of Texas M. D. Anderson Cancer Center from September 2004 to May 2008. CTC were detected and enumerated using the CellSearch system (Veridex LLC, Rariten NJ, USA). Patients were categorized according to first follow-up CTC counts as having a favorable (< 5 CTC/7.5 mL of blood) or unfavorable (≥ 5 CTC) outcome. Reassessment of disease status by CTC count and FDG-PET/CT was performed approximately 2-3 months after initiation of the new treatment, depending on treatment type and schedule. Progression-free survival (PFS) and overall survival (OS) were estimated by Kaplan-Meier product limit method, and compared between groups with the log-rank test.Results: In 54 evaluable patients, the median overall survival time was 17 months (range, 3 to >36). Follow-up CTC levels and FDG-PET/CT response predicted both PFS (p = 0.02 and p = 0.0001, respectively) and OS (p = 0.01 and p = 0.02, respectively), while baseline CTC predicted neither PFS (p = 0.8) nor OS (p = 0.76). In patients with either CTC or FDG-PET/CT response PFS has been 13 months, while in patients with discordant CTC and FDG-PET/CT response PFS has been 6 months and in patients with neither CTC nor FDG-PET/CT response PFS has been 5 months (p = <0.00002). In patients with either CTC or FDG-PET/CT response, OS has not been reached (>31 months); in patients with discordant CTC and FDG-PET/CT response, OS has been 24 months; and in patients with neither CTC nor FDG-PET/CT response, OS has been 18 months (p = 0.02).Conclusions: CTC and FDG-PET/CT are useful tools for therapeutic monitoring of bone metastases from breast cancer. Prospective studies in this specific clinical context are needed to assess the critical roles that CTC and FDG-PET/CT individually as well as collectively play in the prognostic and therapeutic monitoring of bone metastases from breast cancer.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 1109.

2009