Assessment of intratumor hypoxia by integrated (18)F-FDG PET / perfusion CT in a liver tumor model

OBJECTIVES: Hypoxia in solid tumors occurs when metabolic demands in tumor cells surpass the delivery of oxygenated blood. We hypothesize that the (18)F-fluorodeoxyglucose ((18)F-FDG) metabolism and tumor blood flow mismatch would correlate with tumor hypoxia. METHODS: Liver perfusion computed tomography (CT) and (18)F-FDG positron emission tomography (PET) imaging were performed in twelve rabbit livers implanted with VX2 carcinoma. Under CT guidance, a fiber optic probe was inserted into the tumor to measure the partial pressure of oxygen (pO(2)). Tumor blood flow (BF) and standardized uptake value (SUV) were measured to calculate flow-metabolism ratio (FMR). Tumor hypoxia was further identified using pimonidazole immunohistochemical staining. Pearson correlation analysis was performed to determine the correlation between the imaging parameters and pO(2) and pimonidazole staining. RESULTS: Weak correlations were found between blood volume (BV) and pO(2) level (r = 0.425, P = 0.004), SUV and pO(2) (r = -0.394, P = 0.007), FMR and pimonidazole staining score (r = -0.388, P = 0.031). However, there was stronger correlation between tumor FMR and pO(2) level (r = 0.557, P < 0.001). CONCLUSIONS: FMR correlated with tumor oxygenation and pimonidazole staining suggesting it may be a potential hypoxic imaging marker in liver tumor.