Prognostic and therapeutic indicator of fluoroboronophenylalanine positron emission tomography in patients with gliomas.

PURPOSE Boron neutron capture therapy (BNCT) for the treatment of brain tumors has attracted attention recently, and its clinical application has been progressing. We have focused on the use of BNCT with 10B-boronophenylalanine, which preferentially delivers boron-10 atoms to malignant cells through the amino acid transport system. In the present study, we evaluated the long-term outcomes of treatments using 18F-10B-fluoroboronophenylalanine (FBPA), which is an analogue of 10B-boronophenylalanine, by investigating the prognostic significance of the metabolic values and ratios of FBPA as determined by positron emission tomography (PET) in patients with gliomas. EXPERIMENTAL DESIGN Our subjects were 22 patients who underwent an FBPA-PET study and were followed for at least 4 months thereafter. PET parameters, such as the rate constants K1, k2, k3, and k4, were measured before treatment. Data regarding the tumors, the contralateral normal region, and the uptake ratio of FBPA between the tumor and normal tissue 40 min after injection of the tracer were compared with survival rates after the PET treatment. The survival time and the prognostic factors were tested using a Kaplan-Meier survival curve and Cox regression analysis, respectively. RESULTS Among the clinical parameters, the histological grade of a tumor influences survival significantly. When the survival of patients with PET parameters or ratios above the median was compared with that of patients with parameters or ratios below the median, the most significant PET parameter was the K1 value of the tumor. Median survival in patients with a tumor K1 value of 0.033 ml/min (median value) or higher was 11 months, which was significantly shorter than the 77 months in patients with a K1 value below the median (P=0.0006 by generalized Wilcoxon test). CONCLUSIONS The kinetic constants of FBPA metabolism as determined by PET can be of ancillary significance in predicting the prognosis and indicating the feasibility of BNCT in patients with gliomas. The mean survival time was significantly shorter in patients with high uptakes of FBPA. A contributing factor is the K1 value, which reflects amino acid transport activity. FBPA-PET images can allow clinicians to develop treatment plans that are better tailored to the clinical features of their patients.