[Tc-99m]-sestamibi uptake and washout in locally advanced breast cancer are correlated with tumor blood flow

Objectives: To determine the influence of breast tumor blood flow on MIBI kinetics, we compared MIBI uptake and washout to [O-15]-water PET estimates of blood flow in patients with locally advanced breast cancer. Methods: Prior to therapy, 37 patients underwent MIBI and [O-15]-water PET imaging; 22/37 also had MIBI washout analysis. Twenty-five patients underwent serial imaging over the course of chemotherapy. Results: MIBI uptake and blood flow had a significant positive correlation pre-therapy. The change in MIBI uptake over the course of therapy also correlated with the change in blood flow. The half-time of MIBI washout inversely correlated with blood flow, indicating faster MIBI washout with higher blood flow. Conclusions: Blood flow strongly influences early MIBI uptake and can be a factor affecting the rate of MIBI washout in breast tumors. We present a model of MIBI kinetics in tumors which forms a hypothesis for further mechanistic studies of MIBI uptake and washout in breast cancer.