Hypoxia in human gliomas: demonstration by PET with fluorine-18-fluoromisonidazole

Positron emission tomography (PET) with the hypoxic-cell tracer [18F]fluoromisonidazole presents a possible means of noninvasively demonstrating tumor hypoxia. PET studies using this tracer were performed in three patients with malignant glioma, and in all patients the tumor was clearly seen at 5 min postinjection and initial tumor activity exceeded cortical activity. In one patient, there was no tumor retention of [18F] fluoromisonidazole and tumor activity fell while cortical activity increased, with the two tissues reaching equality at 40-50 min. The tumor-to-plasma ratio was 0.71 at 3 hr. The other two patients showed variable tumor retention of [18F]fluoromisonidazole, with tumor-to-plasma ratios of 1.10 and 1.49 at 2 and 3 hr. These results demonstrate the feasibility of using [18F]fluoromisonidazole PET to detect hypoxia in human gliomas in vivo. Clinical trials are needed to determine whether a relationship exists between [18F]fluoromisonidazole uptake and tumor radiation response.