Radiation Pneumonitis Caused by a Migrated Brachytherapy Seed Lodged in the Lung

We report a case of radiation pneumonitis caused by a migrated seed lodged in the lung after prostate brachytherapy. A 71-year-old man underwent transperineal interstitial permanent prostate brachytherapy for localized prostate cancer. On the day after brachytherapy, a routine postimplant chest X-ray revealed migration of one seed to the lower lobe of the left lung. After 1 month, pulmonary opacities were observed in the left lower lobe but not near the seed. He was diagnosed with bacterial pneumonia, and antibiotic therapy was commenced. Two months after brachytherapy, the patient’s symptoms, laboratory data and pulmonary opacities improved; however, an abnormal shadow (consolidation) developed around the migrated seed. Lung consolidation disappeared almost completely 12 months after brachytherapy without any medical treatment. The abnormal shadow probably represented radiation pneumonitis. To the best of our knowledge, this is the first report of radiation pneumonitis caused by a migrated brachytherapy seed in the lung.