NEIM-05. [GA68]DOTATATE PET/MRI-BASED RADIOSURGICAL RESPONSE ASESSMENT IN MENINGIOMA

Abstract

PURPOSE Postoperative PET/MRI with [68Ga]-DOTATATE can differentiate residual meningioma from postsurgical change, aid in target delineation, and portend a more favorable dosimetry with decreased PTV and organ-at-risk dose. Our purpose was to demonstrate utility of DOTATATE PET/MR for radiosurgical treatment (RT) response assessment in meningiomas. METHODS Patients underwent postoperative radiation treatment planning using DOTATATE PET/MRI as part of our IRB-approved prospective trial. Both DOTATATE PET and gadolinium-enhanced T1 weighted MR imaging were incorporated in RT-planning. All patients underwent follow-up DOTATATE PET/MRI at 6-12 months following completion of radiosurgery. Maximum absolute standardized uptake value (SUV) and SUV ratio (SUVR) of lesion/ superior sagittal sinus SUV were obtained. RANO criteria were applied to determine significance of change in size. Statistical analyses were performed using paired t-tests. RESULTS 13 patients (15% WHO-I, 54% WHO-II, 23% WHO-III, 8% WHO grade unknown) were followed postoperatively with pre- and post-RT DOTATATE PET/MRI. 29 meningiomas were treated. 46% (6/13) of subjects received SBRT and 54% (7/13) received SRS. Post-RT DOTATATE PET/MRI demonstrated a 46.4% SUV decrease (p-value = 0.0001) and a 60.8% SUVR decrease (p-value < 0.0001). Of 21 measurable lesions, the size product decreased by 21%; while this decrease was statistically significant (p-value = 0.0008), it was below the 25% decrease defined as clinically significant by RANO guidelines. To date, all patients remain stable radiographically without evidence of recurrence (mean follow-up post RT: 14 months; range: 6-24 months). CONCLUSIONS DOTATATE PET SUV and SUVR demonstrated marked, significant decrease post radiosurgery. Lesion size decrease was statistically significant but not clinically significant by RANO criteria. DOTATATE PET/MR thus represents a promising approach to aid in response assessment for radiosurgically treated meningiomas. Longer-term follow-up is needed to determine the correlation between the degree of post-RT SUV and/or SUVR decrease and progression-free-survival.