Comparison of ambient dose equivalent and occupational radiation exposure from three kinds of 177Lu-labeled PSMA-targeted radioligand therapies

The 177 Lu-PSMA series of agents is widely used for targeted radionuclide therapy in patients with advanced metastatic castration-resistant prostate cancer. The objective of this study is to assess occupational radiation exposure and ambient dose equivalent for three kinds of 177 Lu-labeled PSMA-targeted radioligand-therapy ( 177 Lu-PSMA-RLT). A total of 17 treatments with 7.4 GBq 177 Lu-PSMA-I&T, 5 treatments with 7.4 GBq 177 Lu-PSMA-617 and 9 treatments with 1.11 GBq 177 Lu-EB-PSMA-617 at Beijing Cancer Hospital between July 2022 and December 2023 were involved in the study. A handheld radiation dosimeter was used to measure the ambient dose equivalent rate at various distances from the patients and at different time points from 0 to 24 h after administration. Occupational radiation exposure doses for medical staffs were measured with electronic personal dosimeters, while ring thermoluminescence dosimeters were used to measure hand doses for nurses. The ambient dose equivalent rates due to 177 Lu-PSMA-I&T at a distance of 1 m from the patients were 12.8 ± 2.0 μSv/h at 4 h post-administration, while those due to 177 Lu -PSMA-617 were 17.8 ± 3.6 μSv/h, and those due to 177 Lu-EB-PSMA-617 were 4.2 ± 0.3 μSv/h. For 177 Lu-PSMA-I&T the mean effective doses of nurses, and physicians were 2.64 μSv, and 1.54 μSv per patient, respectively, those for nurses and physicians due to 177 Lu-PSMA-617 were 0.64 μSv and 0.48 μSv, and those for nurses and physicians due to 177 Lu-EB-PSMA-617 were 1.10 μSv and 0.96 μSv. The hand doses for nurses were 184.1 μSv, 134.2 μSv, and 10.2 μSv per patient for 177 Lu-PSMA-I&T, 177 Lu-PSMA-617, and 177 Lu-EB-PSMA-617, respectively. Our findings suggest that all of three kinds of 177 Lu-PSMA-RLT are reasonably safe options for outpatient treatment and the radiation doses received by staff were within the limits of occupational radiation exposure. 177 Lu-EB-PSMA-617 presented a significantly lower risk of radiation exposure to the staff and public. • We compared ambient dose equivalents from Lu-177-PSMA using three ligands: PSMA-I&T, EB-PSMA-617, and PSMA-617. • Lu-177-EB-PSMA-617 indicated a lower radiation risk to medical staff and the public compared to the other treatments. • All three Lu-177-PSMA ligands are safe for outpatient use, with occupational exposure remaining within safety limits.