Abstract
589 Background: Dynamic contrast-enhanced MRI (DCE-MRI) and positron emission tomography (PET) are two imaging modalities previously shown to be predictive of response to neoadjuvant therapy in breast cancer. As the two techniques are functionally very different, the extent of their agreement or discordance for tumor characterization is not well understood. The purpose of this study was therefore to investigate the association between quantitative DCE-MRI enhancement kinetics and 15O-water PET/18F-FDG PET blood flow and metabolic measures of breast tumors. Methods: We retrospectively evaluated exams for 20 patients with locally advanced breast cancer (LABC) who underwent both 15O-water/18F-FDG PET and DCE-MRI. PET measures included 15O-water blood flow, 18F-FDG transport rate constant from blood to tissue (K1), and FDG metabolic rate. DCE-MRI measures included functional tumor volume, initial peak enhancement (PE), and a delayed signal enhancement ratio (SER) assessing washout. Pearson’s correlations and multivariate stepwise regression analyses were performed; p<0.05 was considered significant. Results: PET 15O-water blood flow correlated significantly with DCE-MRI peak SER (r=0.8) and tumor volume (r=0.7). PET K1 measures correlated significantly with DCE-MRI peak PE (r=0.7), peak SER (r=0.6) and tumor volume (r=0.6). By multivariate analysis, SER was the strongest independent MRI correlate of PET blood flow, and PE the strongest MRI correlate for K1. No significant correlations were observed between 18F-FDG PET metabolic rate and the DCE-MRI kinetic parameters. Also, while blood flow and K1 were strongly correlated (r=0.9, p=0.0001), blood flow and metabolic rate were not (r=0.4, p=0.12). Conclusions: The associations between PET and MRI measures may lead to a better understanding of angiogenesis, vascular permeability, and glucose transport in LABC. A lack of correlation of metabolic rate with blood flow and DCE MRI kinetics suggests that 18F-FDG PET provides complimentary metabolic information independent of vascular factors. The combination of MRI and PET may be helpful in understanding tumor pharmacodynamics in response to novel therapy. No significant financial relationships to disclose.
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