sup 68^Ga-NOTA-Aca-BBN (7-14) PET imaging of GRPR in children with optic pathway gliomas

Objectives: Optic pathway glioma (OPG) is a rare neoplasm arising predominantly during childhood. Location in sensitive region involving optic pathways, onset in young patients, and controversial therapy choice make the management still a challenge in pediatric neuro-oncology. Long-term survival can be achieved in children with OPGs by using a tailored treatment in selected patients. However, there is a lack of optimal imaging surveillance or proper visualization of tumor biology at the molecular level of OPGs. This study aims to assess gastrin-releasing peptide receptor (GRPR) targeted PET imaging in children with OPG, also with 18F-FDG PET for comparison and PET/MRI imaging-guided surgery navigation platform application. Methods: Eight children (M 5, F 3, Age range 5-14y, mean age 8.81±4.64) with suspicious optic pathway gliomas, as diagnosed by contrast-enhanced MRI were recruited. Written informed consent was obtained from all patients and legal guardians. Brain PET/CT or PET/MRI acquisitions were performed at 30 min after bolus injection of 68Ga-NOTA-Aca-BBN(7-14) (33.3-90.7 MBq, 1.85 MBq per kilogram of body weight). 4 patients also accepted 18F-FDG brain PET/CT for comparison within 3 days. Regions of interest (ROIs) were drawn manually on the brain lesions using 3D ellipsoid isocontour on each image with the assistance of the corresponding CT and MRI images by two experienced nuclear medicine physicians. Visual assessment and semi-quantitative analysis using SUVmean and SUVmax were used. All the patients underwent surgical removal within 1 week with 68Ga-NOTA-Aca-BBN(7-14) PET-MRI image fusion and navigation platform. After surgical removal, Immunohistochemical staining of tumor samples against GRPR was performed and correlated with 68Ga-NOTA-Aca-BBN(7-14) PET. Results: All 11 lesions in the 8 patients showed prominent 68Ga-NOTA-Aca-BBN(7-14) probe accumulation with excellent contrast to surrounding normal brain tissue. The SUVmax and SUVmean of all the lesions (n = 11) were 1.82 ± 0.59 and 1.17 ± 0.47, respectively. Tumor-to-background ratios were 28.4 ± 5.59 and 18.3 ± 4.99 based on SUVmax and SUVmean, respectively. The SUVmean and SUVmax on 18F-FDG were calculated to be 4.83 ± 1.51 and 7.92 ± 2.08, respectively. 68Ga-NOTA-Aca-BBN(7-14) showed much better tumor/background ratio (28.4 ± 5.59) over 18F-FDG (0.60 ± 0.07). Fusion images were obtained in all cases successfully in PET-MRI navigation platform for tumor delineation. All lesions were conf