Feasibility of bremsstrahlung dosimetry for direct dose estimation in patients undergoing treatment with 90Y-ibritumomab tiuxetan

Abstract

Based on patient-specific dosimetry, the administered activity may be increased by an average factor of 2.4, indicating that most patients could be undertreated. The relative dosimetry approach based on planar imaging largely underestimates doses relative to reference values. Dosimetry based on planar bremsstrahlung imaging is not a dependable alternative to (111)In dosimetry.

A new pharmacokinetic model for 90Y-ibritumomab tiuxetan based on 3-dimensional dosimetry

“…These figures are slightly lower than published data (5000–10000 mL 29 ). Nevertheless the calculated volumes of distribution (our results and published data) remain small, suggesting a limited distribution outside the blood 29 , 30 (29,30)(28,29). These results can be accounted for by mAb properties such as high molecular mass and hydrophilicity/polarity ratio.…”

“…Although our 5-compartment model is a step forward compared to the previous 2-compartment model, there are clear limitations. First, in dosimetric studies, the data used to delineate organs is usually obtained with few samples: three 31 , 32 , four 30 , five 24 , 33 , 34 or even fewer 35 but this reduced sampling can prove limiting for pharmacokinetic studies. The number of image acquisitions was four (4 hours, 1, 4 and 7 days after infusions) The extrapolation method to determine the amount of blood in organs would have been more precise if imaging had been performed 1 hour after infusion, instead of 4 hours but this is problematic given the possible occurrence of infusion-related reactions to mAb.…”