Radiation safety evaluation for Lu177 therapies in the outpatient hospital setting

3023 Objectives: Lu-177 Lutathera® therapy was approved by the FDA in 2018 to treat unresectable or metastatic neuroendocrine tumors. Currently, Lu-177-PSMA-617 is in phase III of clinical evaluation for metastatic castration resistant prostate cancer. Depending on the treatment plan, patients receive multiple Lu-177 treatments over a period of time and can be in the department for up to six hours for each treatment. Lu-177 emits both beta and gamma radiation, presenting several radiation safety concerns. The purpose of the evaluation was to determine radiation safety precautions for the infusion of Lu-177 therapies in the outpatient hospital setting. Methods: Lu-177 research and clinical therapies have been administered for approximately 18 months in our newly designed therapy suite. During this time the Radiation Safety department has been able to determine an effective approach for performing Lu-177 therapies in the outpatient setting to minimize contamination and reduce exposure to the care team. With over 200 Lu-177 therapies administered in our new therapy suite over the past 18 months, the Radiation Safety Department was able to determine an effective method for preparing the therapy room and bathroom to minimize contamination on permanent surfaces. Different absorbent material and toilet coverings were evaluated to determine which worked best at absorbing and preventing the spread of contamination in our facility. Surveys were initiated at the end of each treatment to measure potential contamination. The surveys were performed using a Ludlum 14C survey meter with pancake probe and by collecting multiple wipe samples to verify removable contamination was not present. The wipe samples were analyzed using a Packard Cobra II Auto-Gamma Counter. Syringe shield evaluation for Lu-177 was conducted using two different commercially available syringe shields. The shielding evaluation was performed by measuring the radiation dose, using thermoluminescent dosimeters (TLD), for two unit doses of Lu-177-PSMA-617 with activities of 166 mCi and 205 mCi. Two TLDs were placed on each unshielded syringe and exposed for 15 minutes and removed. Each unit dose was placed in a Biodex Beta Syringe Shield and a Pro-Tec III Syringe Shield with 2 TLDs positioned on the outside of each shield for 15 minutes. One TLD was used as a control. The TLDs were sent to Landauer Inc. for measurement. The results were multiplied by four to determine the dose per hour. Results: Versi-Dry® lab soaker with a waterproof backing provided ample absorbency for covering the bathroom floor and the floor around the injection area of the therapy room for minor spills and small bladder accidents. Disposable chux pads worked well at absorbing fluids around the floor of the toilet and the walls. The toilet seat was covered with plastic wrapping, to minimize the contamination of the seat. The average radiation dose rate from the unshielded syringes for Lu-177-PSMA-617 with an activity of 166 mCi and 205 mCi were 18160 mrem/hr and 22700 mrem/hr, respectively. The radiation dose rate from the 166 mCi and the 205 mCi doses in the Biodex Beta Syringe Shield averaged 520 mrem/hr and 560 mrem/hr, respectively. The radiation dose rate from the 166 mCi and the 205 mCi doses in the Pro-Tec III Syringe shield averaged 720 mrem/hr and 1040 mrem/hr, respectively. Conclusions: Effective prepping of the therapy room and bathroom will ensure easy cleanup and minimal decontamination efforts from the Radiation Safety staff. The Biodex Beta Syringe Shield is more effective at attenuating radiation than the Pro-Tec III Syringe Shield for Lu-177 therapy administrations.