Blood flow and metabolism in locally advanced breast cancer: relationship to response to therapy.

UNLABELLED: Locally advanced breast cancer (LABC) is commonly treated with neoadjuvant chemotherapy followed by definitive surgery. The factors influencing the response of LABC to presurgical chemotherapy are incompletely understood. To characterize in vivo tumor biology in patients with LABC, we measured pretherapy blood flow and glucose metabolism in LABC, compared measurements with clinical and pathologic parameters, and examined blood flow and response to subsequent neoadjuvant chemotherapy. METHODS: Thirty-seven patients with newly diagnosed LABC underwent (18)F-FDG and (15)O-water PET imaging. Thirty-one of these patients underwent neoadjuvant chemotherapy, and response was evaluated by serial measurements of tumor size and pathologic examination after definitive surgery after chemotherapy. Tumor metabolism was estimated from graphic analysis of dynamic (18)F-FDG studies and was expressed as the metabolic rate of (18)F-FDG (MRFDG). Blood flow was estimated from dynamic images after bolus (15)O-water injection using a 1-compartment model. Tumor blood flow and metabolism were compared with clinical and pathologic parameters and with response to chemotherapy. RESULTS: Both blood flow and metabolism were significantly higher in tumor than in normal breast. Tumor blood flow and metabolism were correlated but highly variable. There were weak associations of metabolism with patient age and tumor grade and of blood flow with estrogen receptor status. There was a statistically significant trend for patients with a high MRFDG to have a poorer response to therapy (P = 0.001). Response was not significantly correlated with any other parameters. A low ratio of MRFDG to blood flow was the best predictor of macroscopic complete response (CR) (P = 0.02 vs. non-CR). Preliminary analysis of patient follow-up showed the ratio of MRFDG to blood flow to also be predictive of disease-free survival. CONCLUSION: Despite uniformly large tumor size, blood flow and metabolism in LABC are highly variable. High glucose metabolism predicts a poor response to neoadjuvant chemotherapy, and low MRFDG relative to blood flow is a predictor of CR. Further work is needed to elucidate the biologic mechanisms underlying these findings.

[18F]-2-fluoro-2-deoxyglucose transport kinetics as a function of extracellular glucose concentration in malignant glioma, fibroblast and macrophage cells in vitro.

FDG-PET is used to measure the metabolic rate of glucose. Transport and phosphorylation determine the amount of hexose analog that is phosphorylated and trapped. Competition occurs for both events, such that extracellular glucose concentration affects the FDG image. This study investigated the effect of glucose concentration on the rate of FDG accumulation in three cell lines. The results show that extracellular glucose concentration has a greater impact on the rate of FDG accumulation than the relative abundance of GLUT transporter subtypes.

[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.