Abstract
PURPOSE: An important assumption in dosimetry prior to radionuclide therapy is the equivalence of pretherapeutic and therapeutic biodistribution. In this study the authors investigate if this assumption is justified in sst2-receptor targeting peptide therapy, as unequal amounts of peptide and different peptides for pretherapeutic measurements and therapy are commonly used. METHODS: Physiologically based pharmacokinetic models were developed. Gamma camera and serum measurements of ten patients with metastasizing neuroendocrine tumors were conducted using (111)In-DTPAOC. The most suitable model was selected using the corrected Akaike information criterion. Based on that model and the estimated individual parameters, predicted and measured (90)Y-DOTATATE excretions during therapy were compared. The residence times for the pretherapeutic (measured) and therapeutic scenarios (simulated) were calculated. RESULTS: Predicted and measured therapeutic excretion differed in three patients by 10%, 31%, and 7%. The measured pretherapeutic and therapeutic excretion differed by 53%, 56%, and 52%. The simulated therapeutic residence times of kidney and tumor were 3.1 +/- 0.6 and 2.5 +/- 1.2 fold higher than the measured pretherapeutic ones. CONCLUSIONS: To avoid the introduction of unnecessary inaccuracy in dosimetry, using the same substance along with the same amount for pretherapeutic measurements and therapy is recommended.
Original language | English |
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Pages (from-to) | 5708-5717 |
Number of pages | 10 |
Journal | Medical Physics |
Volume | 39 |
Issue number | 9 |
DOIs | |
Publication status | Published - Sept 2012 |
Keywords
- PBPK modeling
- PRRT
- Y-90-DOTATATE
- dosimetry
- therapy planning
- AKAIKE INFORMATION CRITERION
- PHARMACOKINETIC MODEL
- SOMATOSTATIN ANALOG
- ANTI-CD45 ANTIBODY
- MOLECULAR-SIZE
- TUMOR UPTAKE
- DOSIMETRY
- BIODISTRIBUTION
- RADIOIMMUNOTHERAPY
- AFFINITY