title: Biologically effective dose in fractionated molecular radiotherapy--application to treatment of neuroblastoma with (131)I-mIBG.
abstract: In this work, the biologically effective dose (BED) is investigated for fractionated molecular radiotherapy (MRT). A formula for the Lea-Catcheside G-factor is derived which takes the possibility of combinations of sub-lethal damage due to radiation from different administrations of activity into account. In contrast to the previous formula, the new G-factor has an explicit dependence on the time interval between administrations. The BED of tumour and liver is analysed in MRT of neuroblastoma with (131)I-mIBG, following a common two-administration protocol with a mass-based activity prescription. A BED analysis is also made for modified schedules, when due to local regulations there is a maximum permitted activity for each administration. Modifications include both the simplistic approach of delivering this maximum permitted activity in each of the two administrations, and also the introduction of additional administrations while maintaining the protocol-prescribed total activity. For the cases studied with additional (i.e. more than two) administrations, BED of tumour and liver decreases at most 12% and 29%, respectively. The decrease in BED of the tumour is however modest compared to the two-administration schedule using the maximum permitted activity, where the decrease compared to the original schedule is 47%.
authors.affiliation: Department of Medical Radiation Physics, Clinical Sciences Lund, Lund University, 22185 Lund, Sweden. Department of Medical Physics, Gurutzeta/Cruces University Hospital, 48903 Barakaldo, Spain.
authors.forename: Pablo
authors.initials: P
authors.lastname: Mínguez
authors.forename: Johan
authors.initials: J
authors.lastname: Gustafsson
authors.forename: Glenn
authors.initials: G
authors.lastname: Flux
authors.forename: Katarina Sjögreen
authors.initials: KS
authors.lastname: Gleisner
mesh_terms: D019797:3-Iodobenzylguanidine / Q000627:therapeutic use*; D000465:Algorithms; D019583:Dose Fractionation, Radiation; D006801:Humans; D009447:Neuroblastoma / Q000532:radiotherapy*; D019275:Radiopharmaceuticals / Q000627:therapeutic use*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012062:Relative Biological Effectiveness
chemical_list: D019275:Radiopharmaceuticals; D019797:3-Iodobenzylguanidine