Patient-Specific Dosimetry in Radioligand Therapy (RLT) for Metastatic Prostate Cancer Using 177Lu-DKFZ-PSMA-617

Purpose 177 Lu-DKFZ-PSMA-617 is a promising treatment for patients with metastatic prostate cancer. Specific dosimetry for each patient is an important factor in planning the patient’s treatment process. This study aimed to perform an image-based absorbed dose calculation for the treatment of metastatic prostate cancer with 177 Lu-DKFZ-PSMA-617. Methods The individualized patient dosimetry calculations were based on whole-body planar scintigraphy images acquired in 10 patients with a mean age of 71.4 ± 6.07 years (range 63–85 years) at approximately 0–2 h, 4–6 h, 18–24 h, and 36–48 h after administration of the mean 6253 ± 826.4 MBq (range 5500–7400 MBq) of 177 Lu-DKFZ-PSMA-617. Time-activity curves were generated for various organs. For count conversion to activities, calibration factors were calculated. Finally, the absorbed dose for an individual cycle was calculated using IDIAC-DOSE 2.1 software. Results On average, the calculated absorbed dose for the kidneys and salivary glands were 0.46 ± 0.09 mGy/MBq and 0.62 ± 0.07 mGy/MBq, respectively . Conclusions Based on the results, the 177 Lu-PSMA-617 therapy is a safe method for the treatment of castration-resistant prostate cancer patients. Large inter-individual variations in organ dose were found, demonstrating the need for patient-specific dosimetry and treatment planning.