Dosimetry of [¹⁷⁷Lu]Lu-PSMA therapy in a hemodialysis patient: a case study

Background: In this case study, we share our experience on the treatment of a patient with [¹⁷⁷Lu]Lu-PSMA for metastatic castration-resistant prostate cancer and comorbid kidney failure. Since a poor kidney function impacts [¹⁷⁷Lu]Lu-PSMA clearance, the aim of this study was to carefully monitor the radiation dose to the organs-at-risk, and measure the activity distribution during hemodialysis sessions, by imaging, blood sampling and dialysate sampling. Case presentation: A 72-year-old patient received a total of five cycles of approximately 7.4 GBq [¹⁷⁷Lu]Lu-PSMA-I&T, with an interval of 5–7 weeks per cycle. The radiation dose per cycle (mean ± SD) was measured for different regions: total body 0.51 ± 0.06 Gy, liver (incl. tumours) 5.6 ± 0.5 Gy, kidney (single, poor function) 3.3 ± 0.4 Gy, salivary glands 5.5 ± 0.7 Gy, and bone marrow 0.41 ± 0.07 Gy. Hemodialysis was continued three times a week. Precautions for radiation protection were taken for the first hemodialysis session 20 h after [¹⁷⁷Lu]Lu-PSMA administration, which took place at the radioligand therapy nursery unit. Blood and dialysate samples, collected during hemodialysis, showed a drop of the activity concentration in the blood of the patient (32% in 3 h), and a partial return of activity to the blood (rebound effect) after the end of the hemodialysis treatment. The radiation dose to the bone marrow of the hemodialysis patient was elevated (by a factor of two as compared to literature), but stayed below dose thresholds for severe deterministic side effects. Conclusions: Despite the preexisting kidney failure of a hemodialysis patient, the carefully monitored radiation dose of [¹⁷⁷Lu]Lu-PSMA therapy remained below safe dose thresholds and no signs of severe hematotoxicity were observed.