A preliminary study of the prognostic value of proton magnetic resonance spectroscopic imaging in gamma knife radiosurgery of recurrent malignant gliomas

OBJECTIVE: The goal of this study was to investigate the use of proton magn etic resonance spectroscopic imaging as a prognostic indicator in gamma kni fe radiosurgery of recurrent gliomas. METHODS: Thirty-six patients with recurrent gliomas were studied with proto n magnetic resonance spectroscopic imaging at the time of radiosurgery, and with conventional magnetic resonance imaging examinations at regular time intervals until the initiation of a new treatment strategy. Patients were c ategorized on the basis of their initial spectroscopic results, and their p erformance was assessed in terms of change in contrast-enhancing volume, ti me to further treatment, and survival. RESULTS: The trends in the overall population were toward more extensive in crease in the percent contrast-enhancing volume, a decreased time to furthe r treatment, and a reduced survival time for patients with move extensive i nitial metabolic abnormalities. Statistical analysis of the subpopulation o f patients with glioblastoma multiforme found a significant increase in rel ative contrast-enhancing volume (P < 0.01, Wilcoxon signed-rank test), a de crease in time to further treatment (P < 0.01, log-rank test), and a reduct ion in survival time (P < 0.01, log-rank test) for patients with regions co ntaining tumor-suggestive spectra outside the gamma knife target, compared with patients exhibiting spectral abnormalities restricted to the gamma kni fe target. Further studies are needed to establish statistical significance for patients with lower-grade lesions and to confirm the results observed in this study. CONCLUSION: The pretreatment spectroscopic results provided information tha t was predictive of outcome for this patient pool, both in local control (c hange in contrast-enhancing volume) and global outcome (time to further tre atment and survival). This modality may have an important role in improving the selection, planning, and treatment process for glioma patients.