Prediction of 1cm dose-equivalent rate on the day after administration of 177Lu-DOTATATE from 111In-somatostatine receptor scintigraphy prior to treatment.

Abstract

When patients administered 177Lu-DOTATATE are released or discharged from rooms where radiopharmaceuticals are used, the time required for release or discharge varies across patients. This study investigated whether the amount of radioactivity accumulated on 111In-somatostatine receptor scintigraphy (111In-SRS) performed prior to treatment can predict the 1cm dose-equivalent rate at a distance of 1m from the patient on the day after 177Lu-DOTATATE administration. Whole-body planar 111In-SRS images were acquired for 21 patients. Pixel values within whole-body and abdominal (35 × 25cm) regions of interest (ROIs) were converted to radioactivity dose (MBq). The 1cm dose-equivalent rate (µSv/h) at a distance of 1m from the patient 18.3 ± 0.5h after administration of 177Lu-DOTATATE was measured using an ionization survey meter. The following relationships were observed between the radioactivity on 111In-SRS and the 1cm dose-equivalent rate on the day after administration of 177Lu-DOTATATE: whole-body ROI: y = 0.16x + 5.01 (r = 0.56, p = 0.009), abdominal ROI: y = 0.27x + 5.13 (r = 0.63, p = 0.002). The regression equations indicate that patients cannot be released or discharged from the radiopharmaceutical room the day after 177Lu-DOTATATE administration if the whole-body and abdominal ROI doses are greater than 81 and 48MBq, respectively, on 111In-SRS. The amount of radioactivity accumulated on 111In-SRS may be a predictor of release criteria for patients receiving 177Lu-DOTATATE.