Composite MET-PET Fusion MRI is a Novel Method to Determine Adjuvant Therapy for Growth Hormone Secreting Adenomas

Abstract

Background: Normalization of abnormal Growth Hormone (GH) and Insulin-like Growth Factor (IGF)-1 secretion is essential for the treatment of acromegaly. Although the diagnostic accuracy of magnetic resonance imaging (MRI) has increased in recent years, MRI may fail to detect residual adenoma, even in patients with high IGF-1 levels. The recently developed composite methionine (MET)-PET fusion 3 Tesla (3T)-MRI technique has helped us to determine the location of adenomas that could not be detected by conventional MRI. Regions with high MET uptake are suggestive of residual adenomas. In this study, we sought to confirm the positional relationship between regions of high MET uptake and the sites of viable residual adenoma cells. Methods:We analyzed the results of six patients who underwent gamma knife radiosurgery or re-operation as adjuvant therapy with the aid of composite MET-PET fusion MRI.Results: Based on our experiences in these six patients, composite MET-PET fusion 3T-MRI is useful to plan surgery, and to plan the dose and area of radiation required for gamma knife radiosurgery of an active lesion. Conclusion:The use of composite MET-PET fusion 3T-MRI and subsequent dose planning enabled us to achieve a high remission rate with adjuvant therapy for patients with acromegaly, because MET-PET could clearly detect and delineate the residual tumor.