⁹⁰Y-DOTATOC Dosimetry-Based Personalized Peptide Receptor Radionuclide Therapy

Area of Science:

• Nuclear Medicine
• Radiopharmaceutical Therapy
• Medical Imaging

Background:

• Pretherapy ⁸⁶Y-DOTATOC PET is the gold standard for ⁹⁰Y-DOTATOC dosimetry but faces limitations in clinical use due to cost and availability.
• A feasible and practical dosimetry method is needed for ⁹⁰Y-DOTATOC therapy to optimize patient treatment and minimize toxicity.

Purpose of the Study:

• To develop and validate a dosimetry method for ⁹⁰Y-DOTATOC therapy using ⁹⁰Y-DOTATOC PET/CT and bremsstrahlung SPECT/CT.
• To assess if dosimetry-guided administered activities differ significantly from standard activities.

Main Methods:

• Prospective phase 2 trial involving ⁹⁰Y-DOTATOC therapy in patients with somatostatin receptor-positive tumors.
• Dosimetry determined using serial time-of-flight ⁹⁰Y-DOTATOC PET/CT and bremsstrahlung SPECT/CT scans post-therapy.
• Renal radiation dose calculated from time-integrated activity and kidney mass, with activity adjusted to limit kidney and bone marrow doses.

Main Results:

• Renal radiation dose per cycle varied significantly among patients (0.32–3.0 mGy/MBq).
• In 85% of adult patients, administered activity was adjusted by at least 20% in subsequent cycles based on dosimetry.
• The developed dosimetry method is feasible and impactful for tailoring ⁹⁰Y-DOTATOC therapy.

Conclusions:

• Renal dosimetry of ⁹⁰Y-DOTATOC is achievable using combined ⁹⁰Y-DOTATOC PET/CT and bremsstrahlung SPECT/CT.
• This dosimetry approach significantly influences administered activity, enabling personalized treatment cycles.
• The method provides a practical alternative to ⁸⁶Y-DOTATOC pretherapy dosimetry for optimizing ⁹⁰Y-DOTATOC therapy.