Gamma camera image of patient 7 (anterior and posterior) 24 h after injection.
The peptides are administered into the central compartment, distributed via blood flow and flow to interstitial spaces. Specific binding, internalization, and degradation take place in sst2 positive organs. The peptide is rapidly excreted via the kidneys. The model consists of two equal systems (labeled and unlabeled substance) which are connected by competition for the same receptors and by physical decay.
Investigated kidney models. Model A: unspecific uptake and release of intact peptide into the serum. Model B: unspecific uptake by kidney cells with subsequent degradation. Model C: no unspecific uptake, a fraction of peptide flows directly back to kidneys serum. Model D: no unspecific uptake, all peptide flows from the kidneys to bladder.
Models A–D were fitted to biodistribution data (111In-DTPAOC) of the liver, spleen, kidney, total body, tumor, and serum. The AICc was used to select the kidney model which was most supported by the data. Measured and simulated excretions (N = 3) of 90Y-DOTATATE were compared. The pretherapeutic and therapeutic AUCs of all organs were calculated. For the therapeutic AUC simulations based on the fitted parameters and the amounts of actually injected 90Y-DOTATATE were conducted. The influence of the amount of 90Y-DOTATATE was investigated.
A: Fitted organ curves (model A2) of patient 3. B: Fitted tumor curves (model A2) of patients 6–10.
Residence times of organs normalized to organ mass for (a) tumor perfusion (2 l/min/l tumor volume) and 0.033 l tumor volume and (b) tumor perfusion (0.01 l/min/l tumor volume) and 1.3 l tumor volume.
Patient characteristics and treatment.
Model set and Akaike weights.
Estimated parameters of organs.
Estimated tumor parameters.
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