High-uptake areas on positron emission tomography with the hypoxic radiotracer (18)F-FRP170 in glioblastomas include regions retaining proliferative activity under hypoxia

OBJECTIVE: The aim was to evaluate the proliferative activity of high-uptake areas on positron emission tomography (PET) with the hypoxic cell radiotracer, 1-(2-[(18)F]fluoro-1-[hydroxymethyl]ethoxy)methyl-2-nitroimidazole (FRP170). METHODS: Thirteen patients with glioblastoma underwent FRP170 PET before tumor resection. During surgery, tumor specimens were stereotaxically obtained from regions corresponding to high (high-uptake areas, HUAs) and relatively low (low-uptake areas, LUAs) accumulation of FRP170. We compared immunohistochemical staining for Ki-67 and hypoxia-inducible factor (HIF)-1α between HUA and LUA. RESULTS: HIF-1α index was significantly higher in HUAs than in LUAs. In contrast, mean Ki-67 indices did not differ significantly between HUAs and LUAs. CONCLUSIONS: Findings for HIF-1α index clearly indicated that HUAs on FRP170 PET represented hypoxic regions in glioblastoma. However, findings of Ki-67 index suggest that HUAs on FRP170 PET include regions retaining proliferative activity regardless of tissue hypoxia.