Blood clearance and occupational exposure for 177Lu-DOTATATE compared to 177Lu-PSMA radionuclide therapy.

Abstract

The main target of this work is to examine blood clearance and external exposure for 177Lu-DOTATATE compared with new emerging 177Lu-PSMA therapy. Blood clearance and radiation exposure of 31 patients treated with 5.5 ± 1.1GBq 177Lu-DOTATATE were compared to those of 23 patients treated with 7.4GBq 177Lu-PSMA. Dose rates were measured at several distances and time points up to 120h after treatment. Blood samples were collected conjunctively after infusion. Caregiver's cumulative dose was measured by means of an OSL (optically stimulated luminescence) dosimeter for 4-5days and medical staff's dose was also estimated using electronic personal dosimeters. Finger dose was determined via ring TLD (Thermoluminescence Dosimeter) for radiopharmacists and nurses. Dose rates due to 177Lu-DOTATATE at a distance of 1m, 4h and 6h after infusion, were 3.0 ± 2.8 and 2 ± 1.9µSv/(hGBq), respectively, while those due to 177Lu-PSMA were 3.1 ± 0.8 and 2.2 ± 0.9µSv/(hGBq). Total effective dose of 17 caregivers was 100-200µSv for 177Lu-DOTATATE therapy. Mean effective doses to nurses and radiopharmacists were 5 and 4µSv per patient, respectively, while those for physicists and physicians were 2µSv per patient. For 177Lu-DOTATATE, effective half-life in blood and early elimination phase were 0.31 ± 0.13 and 4.5 ± 1h, while they were found as 0.4 ± 0.1 and 5 ± 1h, respectively, for 177Lu-PSMA. The first micturition time following 177Lu-DOTATATE infusion was noted after 36 ± 14min, while the second and third voiding times were after 74 ± 9 and 128 ± 41min, respectively. It is concluded that blood clearance and radiation exposure for 177Lu-DOTATATE are very similar to those for 177Lu-PSMA, and both treatment modalities are reasonably reliable for outpatient treatment, since the mean dose rate [2.1µSv/(hGBq)] decreased below the dose rate that allows release of the patient from the hospital (20µSv/h) after 6h at 1m distance.