A five-compartment biokinetic model for ⁹⁰ Y-DOTATOC therapy

Area of Science:

• Nuclear Medicine
• Radiopharmaceutical Therapy
• Biokinetics Modeling

Background:

• Neuroendocrine tumors (NETs) are treated with somatostatin receptor-binding peptides like 90Y-DOTATOC.
• Accurate dosimetry is crucial for optimizing targeted radiopeptide therapy efficacy and safety.

Purpose of the Study:

• Develop a biokinetic model for 90Y-DOTATOC to estimate absorbed doses in kidneys and tumors.
• Determine patient-specific transfer coefficients and time-activity curves.

Main Methods:

• A multi-compartment model with differential equations was developed for infusion and post-infusion periods.
• Activities were measured in blood and urine; transfer coefficients were fitted to time-activity data.
• Monte Carlo simulations were used to determine absorbed dose fractions.

Main Results:

• Patient-specific transfer coefficients and time-activity curves for 90Y-DOTATOC were determined for 14 patients.
• Mean absorbed dose per unit activity in kidneys was 1.43 mGy/MBq (range 0.73-2.42 mGy/MBq).
• Mean absorbed dose per unit activity in tumors was 30.94 mGy/MBq (range 20.05-42.31 mGy/MBq).

Conclusions:

• The analytical biokinetic model successfully determined transfer coefficients, time-activity curves, and absorbed doses for 90Y-DOTATOC therapy.
• The model is applicable to other radiopharmaceuticals with predominantly urinary excretion.
• This approach aids in personalized dosimetry for targeted radiopeptide therapies.