Exhalation of Rn-219 by patients treated with Radium-223.

Area of Science:

• Radiochemistry and Nuclear Medicine
• Oncology and Cancer Therapy
• Radiation Safety and Dosimetry

Background:

• Radium-223 (Ra-223) dichloride is an approved treatment for castration-resistant prostate cancer (CRPC) with bone metastases.
• The direct progeny of Ra-223 is Radon-219 (Rn-219), a radioactive noble gas that can be exhaled by patients.
• Assessing patient and potential family member radiation exposure from Rn-219 exhalation is crucial for outpatient treatment safety.

Purpose of the Study:

• To directly measure Radon-219 (Rn-219) exhalation in patients treated with Radium-223 (Ra-223) dichloride.
• To evaluate the feasibility and patient tolerance of a direct breath measurement method for Rn-219.
• To assess potential radiation exposure risks in an outpatient setting.

Main Methods:

• Utilized Alphaguard radon monitors and custom breath-test kits for direct Rn-219 measurement in exhaled breath.
• Measurements were conducted at two time points post-injection: 20-30 minutes and 3-4 hours.
• Data from 21 administrations in 14 patients were analyzed, with statistical methods applied to censored data.

Main Results:

• Mean Rn-219 activity concentrations in exhaled breath were approximately 4.4 kBq/L at 3-4 hours post-injection.
• Higher expectation values, around 6 kBq/L, were observed at 20-30 minutes post-injection.
• Despite measurement range limitations, statistical analysis confirmed significant Rn-219 exhalation.

Conclusions:

• Direct measurement using Alphaguard instruments is a suitable method for assessing Rn-219 exhalation in Ra-223 treated patients.
• The measurement procedure is well-tolerated by patients.
• The presence of Rn-219 in exhaled breath was confirmed, aligning with indirect measurement findings.