Differences in predicted and actually absorbed doses in peptide receptor radionuclide therapy

Med Phys. 2012 Sep;39(9):5708-17. doi: 10.1118/1.4747266.


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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Humans
  • Models, Biological*
  • Neuroendocrine Tumors / metabolism*
  • Neuroendocrine Tumors / radiotherapy*
  • Octreotide / analogs & derivatives
  • Octreotide / metabolism
  • Octreotide / pharmacokinetics
  • Octreotide / therapeutic use
  • Organometallic Compounds / pharmacokinetics
  • Organometallic Compounds / therapeutic use
  • Pentetic Acid / analogs & derivatives
  • Pentetic Acid / metabolism
  • Pentetic Acid / pharmacokinetics
  • Pentetic Acid / therapeutic use
  • Radiation Dosage*
  • Radiotherapy Dosage
  • Receptors, Somatostatin / metabolism*


  • 90Y-octreotate, DOTA(0)-Tyr(3)-Thr(8)-
  • Organometallic Compounds
  • Receptors, Somatostatin
  • somatostatin receptor sst2A
  • SDZ 215-811
  • Pentetic Acid
  • Octreotide