Dosimetric models and S factors for radiation doses to the bladder wall in children receiving therapeutic iodine-131-MIBG.

With the introduction of [{sup 131}I]metaiodobenzylguanidine (MIBG) therapy for the treatment of neuroblastoma, there is a need for accurate estimation of radiation dose to the urinary bladder in children. Bladder dosimetry is of particular importance when MIBG therapy is part of a combined modality treatment, either in combination with total body external beam irradiation or chemotherapy agents where additive damage to the bladder could become clinically significant. Published information on bladder doses from [{sup 131}I]MIBG is relatively scarce, but there are at least two publications which focus on bladder dosimetry in children, each using a different calculation method. We evaluated these publications in view of our initial experience with the new MIRD urodynamic model since the original publications had errors. The exercise raises doubts about the certainty of S factors previously used in children. 10 refs., 2 tabs.