Radiation precautions for inpatient and outpatient 177Lu-DOTATATE peptide receptor radionuclide therapy of neuroendocrine tumours

Abstract

Background177Lu-DOTATATE peptide receptor radionuclide therapy is administered to patients on an inpatient and outpatient basis for the treatment of well-differentiated, metastatic neuroendocrine tumours. Following administration, these patients present an external radiation hazard due to the gamma emissions of lutetium-177. The purpose of this study was to determine precautions to be observed by 177Lu-DOTATATE patients to restrict the dose received by patients’ family members to less than 5\u2009mSv in 5\u2009years and members of the public to less than 1\u2009mSv per year in line with the current UK legislation. Retrospective data from therapeutic administrations of 177Lu-DOTATATE (Mallinckrodt Pharmaceuticals) and Lutathera® (Advanced Accelerator Applications) were analysed to measure activity retention at discharge. Patient dose rate measurements were assumed to follow the same activity decay curve as that derived from a least squares fit of geometric mean counts in planar whole-body scans performed at four time points post-administration. Combining this with social contact times, the cumulative dose received through contact with the patient was estimated and an iterative process used to determine the length of contact restrictions to ensure the relevant dose constraints are not exceeded.ResultsOn average, 36% of the administered activity was retained at the time of discharge for inpatients receiving 177Lu-DOTATATE (Mallinckrodt). Retentions of 24% and 38% were measured for Lutathera® inpatients and outpatients respectively. Inpatients should restrict day contact and sleep separately from their partner for 15\u2009days and remain off work for 5\u2009days post-therapy. Contact with children for whom the patient is the main carer should be restricted for 16, 13 and 9\u2009days for children below 2, 2–5 and 5–11\u2009years respectively. One additional day is added to outpatient restriction periods, except for children aged 2–5\u2009years which remains 13\u2009days. No private transport restrictions are required. Patients should limit travel by public transport to 1\u2009h on the day of discharge.ConclusionRestrictions are necessary to limit radiation dose to members of patients’ household and the public. Proposed precautions for inpatient and outpatient 177Lu-DOTATATE therapy protocols restrict the dose received to less than the limit imposed by the UK legislation.