(68)Ga-DOTATATE PET-CT as a tool for radiation planning and evaluating treatment responses in the clinical management of meningiomas

BACKGROUND AND PURPOSE: Meningiomas express the somatostatin receptor (SSTR), which normal bone and brain lack. PET imaging with SSTR ligands such as (68) Ga-DOTATATE have been recently shown to aid in the imaging and identification of menginiomas. We hypothesize that (68) Ga-DOTATATE PET/CT in conjunction with MRI aids in radiation (RT) target volume delineation and evaluating treatment response. MATERIALS AND METHODS: Nineteen patients with meningiomas underwent (68) Ga-DOTATATE PET/CT and MRI for RT planning and/or post-treatment follow-up. Meningiomas were grade I (n = 9) or not biopsied (n = 8) and frequently involved base of skull (n = 10). Ten (53%) patients received post-operative RT and 9 (47%) received fractaionted RT. In the subgroup that underwent both pre- and post-RT (68) Ga-DOTATATE PET as well as MRI (n = 10), ROVER (ABX GmbH, Radeberg, Germany) adaptive thresholding software was utilized to measure total lesion activity (mean and max) before and after treatment. Tumor volume based on MRI was calculated before and after treatment. Total lesion activity and tumor volume changes were compared using Wilcoxon signed rank test. RESULTS: (68) Ga-DOTATATE PET/CT identified intraosseous (n = 4, 22%), falcine (n = 5, 26%) and satellite lesions (n = 3, 19%) and clarified the diagnosis of meningioma, resulting in a change in management in three patients. Mean total lesion activity decreased 14.7% (median), from pre to post-RT (68) Ga-DOTATATE PET [range 97–8.5% (25–75%),S = − 26.5, p = 0.0039]. Max total lesion activity decreased 36% (median) over the same period [range 105–15% (25–75%), S = − 26.5 p = 0.0039]. In contrast, meningioma volumes based on MRI measurements did not significantly change per RECIST criteria and Wilcoxon signed rank test (S = − 3, p = 0.7422). CONCLUSION: (68) Ga-DOTATATE PET/CT helped confirm suspected diagnoses and delineate target volumes particularly when lesions involved osseous structures and the falx. Mean and max total tumor (68) Ga-DOTATATE activity on PET/CT decreased at three months following RT despite stable tumor volumes on MRI. Future studies are warranted to (1) assess the sensitivity and specificity of (68) Ga-DOTATATE PET/CT, (2) evaluate the impact of (68) Ga-DOTATATE PET/CT-based planning on treatment outcomes, and (3) assess the prognostic significance of these post-treatment imaging changes.