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

The main target of this work is to examine blood clearance and external exposure for Lu-177-DOTATATE compared with new emerging Lu-177-PSMA therapy. Blood clearance and radiation exposure of 31 patients treated with 5.5 +/- 1.1 GBq Lu-177-DOTATATE were compared to those of 23 patients treated with 7.4 GBq Lu-177-PSMA. Dose rates were measured at several distances and time points up to 120 h 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 4-5 days 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 Lu-177-DOTATATE at a distance of 1 m, 4 h and 6 h after infusion, were 3.0 +/- 2.8 and 2 +/- 1.9 A mu Sv/(h GBq), respectively, while those due to Lu-177-PSMA were 3.1 +/- 0.8 and 2.2 +/- 0.9 A mu Sv/(h GBq). Total effective dose of 17 caregivers was 100-200 A mu Sv for Lu-177-DOTATATE therapy. Mean effective doses to nurses and radiopharmacists were 5 and 4 A mu Sv per patient, respectively, while those for physicists and physicians were 2 A mu Sv per patient. For Lu-177-DOTATATE, effective half-life in blood and early elimination phase were 0.31 +/- 0.13 and 4.5 +/- 1 h, while they were found as 0.4 +/- 0.1 and 5 +/- 1 h, respectively, for Lu-177-PSMA. The first micturition time following Lu-177-DOTATATE infusion was noted after 36 +/- 14 min, while the second and third voiding times were after 74 +/- 9 and 128 +/- 41 min, respectively. It is concluded that blood clearance and radiation exposure for Lu-177-DOTATATE are very similar to those for Lu-177-PSMA, and both treatment modalities are reasonably reliable for outpatient treatment, since the mean dose rate [2.1 A mu Sv/(h GBq)] decreased below the dose rate that allows release of the patient from the hospital (20 A mu Sv/h) after 6 h at 1 m distance.