A One-Year Review of the Radiation Safety Procedures and Protocols for Peptide Receptor Radionuclide Therapy (PRRT) Using Lutetium Lu 177 Dotatate

Abstract

The treatment of gastroenteropancreatic neuroendocrine tumors (GEP-NETs) using drugs known as Peptide Receptor Radionuclide Therapy (PRRT) has been active for 14 months at our institution. The radionuclide used in the PRRT Program is Lutetium Lu 177 dotatate. This research seeks to share the policies and procedures of our radiation safety program, as well as our experiences in the first year of this therapy program. The key guidelines used to establish a radiation safety program include the principle of ALARA (as low as reasonably achievable), the NRC guidelines and any state-specific requirements, the properties of the radionuclide itself, and the management of contamination. Following the calculation formalism outlined in NRC Regulatory Guide 8.39 Release of Patients Administered Radioactive Materials, policy was set to release patients with survey readings at or below 2.1 mR/hr at 1 meter. Patients receive PRRT in a shielded room; the infusion pumps/stands are covered with chuck pads. The primary excretion pathway is through urine, thus absorbent pads are also around the toilet and on the floor of the patient restroom. Vendor estimates of excretion through urine are 58% in the first 24 hours and over 99% in 14 days. The night after the treatment patients either go home or stay in our onsite hotel. Upon checkout from the hotel room, physics staff conducts a room release survey. A Ludlum Model 26 Integrated Frisker calibrated to a collection efficiency of 20%. All linens and surfaces, specifically in the bathroom, are surveyed. If contamination is detected, the following take place: 1. If it is removable (e.g., bed sheet, towel), it is double bagged, labeled, and taken to short term decay. 2. If it is not removable (e.g., toilet, floor in bathroom, chair), it is cleaned and re-measured prior to the room being opened up for a new patient. After noticing the restroom floor was often contaminated, we began lining the floors of all Lu 177 patient restrooms with chuck pads. The rate of restroom floor contamination in the patient rooms has dropped significantly since making this procedural change. To date, 25 patients have received a total of 73 treatments. All were prescribed a 200 mCi dose of Lu 177 dotatate. The actual amount of Lu 177 infused ranged from 191.67-215.106 mCi (mean 202.2 mCi). Time from the start of injection to patient release ranged from 2 hours to 4.68 hours (mean 3.1 hours). Survey readings of patients after injection ranged from 0.54 mR/hr to 4.1 mR/hr (mean 1.5 mR/hr) at 1 meter. From our experience in the first year of this program, contamination risk is best minimized through stringent patient education on care when using the restroom and proper preparation of hotel rooms where patients will stay. Ethical considerations should be made when considering sending patients to local hotels. Also, permissible exposure levels to caregivers should take into account the fact that most patients receive 4 treatments.