Patient-Specific Dosimetry Using Pretherapy [124I]m-iodobenzylguanidine ([124I]mIBG) Dynamic PET/CT Imaging Before [131I]mIBG Targeted Radionuclide Therapy for Neuroblastoma

Abstract

Purpose Iodine-131-m-iodobenzylguanidine ([131I]mIBG) targeted radionuclide therapy (TRT) is a standard treatment for recurrent or refractory neuroblastoma with response rates of 30–40%. The aim of this study is to demonstrate patient-specific dosimetry using quantitative [124I]mIBG PET/CT imaging with a Geant4-based Monte Carlo method for better treatment planning. Procedures A Monte Carlo dosimetry method was developed using the Geant4 toolkit with voxelized anatomical geometry and source distribution as input. The pre-segmented hybrid computational human phantoms developed by the University of Florida and the National Cancer Institute (UF/NCI) were used as a surrogate to characterize the anatomy of a given patient. S-values for I-131 were estimated by the phantoms coupled with Geant4 and compared with those estimated by OLINDA|EXM and MCNPX for the newborn model. To obtain patient-specific biodistribution of [131I]mIBG, a 10-year-old girl with relapsed neuroblastoma was imaged with [124I]mIBG PET/CT at four time points prior to the planned [131I]mIBG TRT. The organ and tumor absorbed dose of the clinical case were estimated with the Geant4 method using the modified UF/NCI 10-year-old phantom with tumors and the patient-specific residence time. Results For the newborn model, the Geant4 S-values were consistent with the MCNPX S- values. The S-value ratio of the Geant4 method to OLINDA|EXM ranged from 0.08 to 6.5 of all major organs. The [131I]mIBG residence time quantified from the pretherapy [124I]mIBG PET/CT imaging of the 10-year-old patient was mostly comparable to those previously reported. Organ absorbed dose for the salivary glands were 98.0 Gy, heart wall, 36.5 Gy, and liver, 34.3 Gy; while tumor absorbed dose ranged from 143.9 Gy to 1641.3 Gy in different sites. Conclusions Patient-specific dosimetry for [131I]mIBG targeted radionuclide therapy was accomplished using pretherapy [124I]mIBG PET/CT imaging and a Geant4-based Monte Carlo dosimetry method. The Geant4 method with quantitative pretherapy imaging can provide dose estimates to normal organs and tumors with more realistic simulation geometry, and thus may improve treatment planning for [131I]mIBG TRT.

Theranostics in nuclear medicine practice

“…In patients with neuroblastoma and pheochromocytoma, [ 123 I]I-mIBG has high sensitivity (97% and 94%) and specificity (up to 96% and 92%), respectively 44–46. If available, [ 124 I]I-mIBG-PET can be equally used for the planning of mIBG targeted therapy 47,48…”

Radiosynthesis of no-carrier-added meta-[124I]iodobenzylguanidine for PET imaging of metastatic neuroblastoma

“…In vivo imaging for the accurate staging and measurement of response to therapy is critical to the risk stratification of patients with neuroblastoma in order to offer the most individually tailored treatment possible. Currently used planar [ 123 I] m IBG scintigraphy does however have disadvantages associated with its poor spatial and anatomical resolution [7, 8]. SPECT has been used to provide better comparison with anatomical imaging data, in particular when images are fused with X-ray computed tomography (CT) or a combined SPECT-CT scanner is available.…”

Impact of Whole-Body Radiation Dose on Response and Toxicity in Patients With Neuroblastoma After Therapy With131I-Metaiodobenzylguanidine (MIBG)

“…Because TSARD was not calculated in our study, this relationship could not be evaluated. Future studies including more accurate tumor dosimetry such as 124 I‐MIBG with PET‐CT technology will improve our assessment of this ratio …”