Estimation of 223Ra in a sewage system of hospital during radiopharmaceutical therapy with 223Ra dichloride (Xofigo®)

Background. Radiopharmaceutical therapy with 223Ra dichloride (Xofigo®) is an effective method of treatment of bone metastases in patients with metastatic castration-resistant prostate cancer. Increased number of radiopharmaceutical therapy procedures with 223Ra requires revision and update of the existing requirements to ensure radiation safety. Current problems in terms of radiation safety during radiopharmaceutical therapy are assessment of radiopharmaceutical excretion from a patient body and radionuclide activity in patient biological waste.Aim. To estimate the activity of 223Ra excreted from a patient body at hospital (during the first hours after radiopharmaceutical administration) and activity concentration in the sewage water of the hospital during radiopharmaceutical therapy with 223Ra dichloride (Xofigo®).Materials and methods. Eleven male patients with metastatic castration-resistant prostate cancer undergoing radiopharmaceutical therapy with 223Ra dichloride were included in the study. Each micturition from patients in four hours had been sampled, and the samples were prepared to measure activity of 223Ra in the urine. The urine sample residue was flushed down a dedicated patient toilet in the Department of Radionuclide Diagnosis and Therapy. Sewage water sampling was performed at three points (at three manholes) of the hospital. The 223Ra activity in urine and sewage water samples was measured using a gamma semiconductor spectrometer.Results. All urine samples exceeded the threshold value of 223Ra activity concentration and were considered liquid radioactive waste. The activity concentration of 223Ra in the sewage water close to the Department of Radionuclide Diagnosis and Therapy building, and at the point where the sewage water from the building merged with the water from and the nearest building exceeded the threshold value. The activity concentration of 223Ra decreased with increasing sewage water flow in the sewage system, and in the output from the entire hospital the activity concentration in the sewage water samples was below the threshold value.Conclusion. The results of this work show dilution of patient biological waste and reduction of 223Ra activity concentration in the sewage system of a large hospital, which suggest that patient biological waste after radiopharmaceutical therapy with 223Ra dichloride could be disposed directly into the sewage system and a differentiated approach to patient waste management after radiopharmaceutical therapy with 223Ra dichloride could be applied.