Differentiation between radionecrosis and malignant brain tumor recurrence in patients treated by 192Ir HDR brachytherapy: 1H - MRS analysis of the brain metabolic spectrum

Computerized tomography (CT) with contrast infusion and Magnetic Resonance Imaging (MRI) do not differentiate radionecrosis and malignant tumor recurrence. Proton Magnetic Resonance Spectroscopy seems to be a new radiological method that could solve this problem. The aim of the study was to evaluate the usability of 1H - MRS in patients after brachytherapy. Sixty patients were treated by 192Ir HDR brachytherapy because of malignant brain tumors (gliomas and brain metastases). Prospectively, 4 months after brachytherapy, 24 patients underwent MRI and 1H - MRS examinations. All patients qualified for the prospective study were in good general condition before and after the brachytherapy (Karnofsky Performance Score (KPS) > 60%). Combined assessment of MRI and 1H - MRS gave us the possibility to differentiate the observed pathological changes. In 18 cases (75%) there was a decrease in tumor volume. The tumor infiltration area was larger than the necrotic area in 5 cases. An isolated recurrence mass was observed in only one case. Neurosurgical brain decompression with pathological mass resection was needed in 6 patients with increased intracranial pressure and enhanced neurological deficits. Histopathological examination confirmed the diagnosis revealed in the 1H - MRS examination in each case. Proton Magnetic Resonance Spectroscopy is helpful in evaluating the influence of radiation on the tumor and the surrounding brain tissue. Moreover, it solves the problem of differentiating between radionecrosis and tumor recurrence. (author)