RT Journal Article
SR Electronic
T1 MIRD Dose Estimate Report No. 20: Radiation Absorbed-Dose Estimates for <sup>111</sup>In- and <sup>90</sup>Y-Ibritumomab Tiuxetan
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 644
OP 652
DO 10.2967/jnumed.108.057331
VO 50
IS 4
A1 Darrell R. Fisher
A1 Sui Shen
A1 Ruby F. Meredith
YR 2009
UL http://jnm.snmjournals.org/content/50/4/644.abstract
AB Absorbed-dose calculations provide a scientific basis for evaluating the biologic effects associated with administered radiopharmaceuticals. In cancer therapy, radiation dosimetry supports treatment planning, dose-response analyses, predictions of therapy effectiveness, and completeness of patient medical records. In this study, we evaluated the organ radiation absorbed doses from intravenously administered 111In- and 90Y-ibritumomab tiuxetan. Methods: Ten patients (6 men and 4 women) with non-Hodgkin lymphoma, cared for at 3 different medical centers, were administered the tracer 111In-ibritumomab tiuxetan and assessed using planar scintillation camera imaging at 5 time points and CT–organ volumetrics to determine patient-specific organ biokinetics and dosimetry. Explicit attenuation correction based on the transmission scan or transmission measurements provided the fraction of 111In-administered activity in 7 major organs, the whole body, and remainder tissues over time through complete decay. Time–activity curves were constructed, and radiation doses were calculated using MIRD methods and implementing software. Results: Mean radiation absorbed doses for 111In- and for 90Y-ibritumomab tiuxetan administered to 10 cancer patients are reported for 24 organs and the whole body. Biologic uptake and retention data are given for 7 major source organs, remainder tissues, and the whole body. Median absorbed dose values calculated by this method were compared with previously published dosimetry for ibritumomab tiuxetan and the product package insert. Conclusion: In high-dose radioimmunotherapy, the importance of patient-specific dosimetry becomes obvious when the objective of treatment planning is to achieve disease cures, safely, by limiting radiation dose to any critical normal organ to its maximum tolerable value. Compared with the current package insert, we found differences in median absorbed dose by multiples of 24 in the kidneys, 1.8 in the red marrow, 0.65 in the liver, 0.077 in the intestinal wall, 0.30 in the lungs, 0.46 in the spleen, and 0.34 in the heart wall.