Serial Positron Emission Tomography Imaging of Changes in Amino Acid Metabolism in Low Grade Astrocytoma After Radio- and Chemotherapy —Case Report—

A 37-year-old male with mixed glioma was treated with combined radio and chemotherapy. The amino acid metabolism of the tumor site and normal brain was followed by positron emission tomography using [¹¹C]methionine ([¹¹C]Met). The accumulation of [¹¹C]Met in the tumor decreased during therapy and slightly increased 7 months after completion of the therapy, but then decreased markedly. However, computed tomography revealed no notable changes. The contralateral gray matter also showed a gradual decrease of [¹¹C]Met accumulation. These findings indicate that reduction of amino acid metabolism in the tumor continues after radiochemotherapy although neuroimaging reveals no further morphological changes. Such therapy also has long-term effects on normal brain tissue.