O7.09[68GA]-DOTATATE-PET IMAGING PREDICTS SOMATOSTATIN RECEPTOR II EXPRESSION IN MENINGIOMAS

BACKGROUND: Meningiomas are known to express somatostatin receptors. Positron emission tomography (PET) using the somatostatin receptor II (SSR II) analogue [68Ga]-DOTATATE as a tracer, has recently been introduced for imaging of meningiomas. It was the aim of this study to correlate tracer uptake and somatostatin receptor expression in [68Ga]-DOTATATE-PET-guided biopsies obtained during open resection of meningiomas. METHODS: Adult patients with primary or recurrent meningiomas were prospectively enrolled. Preoperative MRI and [68Ga]-DOTATATE-PET scans were used for neuronavigation which included intraoperative computed tomography for registration. During open resection of meningiomas, navigated biopsies were obtained and the tissue sampling site was documented on both MRI and [68Ga]-DOTATATE-PET scans. A histopathological analysis was done, including determination of SSR II expression by immunohistochemistry. Maximum standardized uptake volume (SUVmax) of PET tracer was measured at the tissue sampling sites and correlated with SSR II expression. Additionally, MRI scans were evaluated for the presence of tumor tissue at the sampling sites. RESULTS: 21 patients were included in our study. 12 patients suffered from primary meningioma, 9 had recurrent meningiomas. The median age was 51 years. A total of 115 samples was obtained and 81 showed tumor tissue whereas 34 showed tumor free tissue on histopathological analysis. PET data showed that a SUVmax >2.3 was significantly associated with a histopathological diagnosis of tumor tissue. PET imaging showed a significantly increased sensitivity regarding the detection of tumor tissue as compared to MRI (p ≤ 0.05). There was no significant difference in specificity (p = 0.4) and positive predictive value (p = 0.3). Statistical analysis of quantitative SSR II expression and SUVmax values showed a highly significant positive correlation (p ≤ 0.01). CONCLUSIONS: [68Ga]-DOTATATE-PET precisely predicts SSR II expression in meningioma tissue. Furthermore, PET detects tumor tissue with higher sensitivity than MRI. Taken together, [68Ga]-DOTATATE-PET appears to be a valuable tool for planning personalized therapy in meningioma patients, e.g. for determining the necessary extent of resection or for defining the optimal radiotherapy target volume.