Pulmonary changes after single dose interstitial brachytherapy for lung tumors

PURPOSE: The reaction of lung tissue to extreme single brachytherapy doses have not been analyzed in the past. METHODS: Overall, 46 lung tumors were treated in 32 patients with HDR (high dose rate) brachytherapy (median dose 20Gy). Treatment planning (n = 46) and follow up CT images (n = 154) performed up to 60 months after brachytherapy were evaluated. RESULTS: The long-term local tumor control was 81%. Pneumonitis was classified as grade 1, 2 and 3 in 26 (57%), 4 (9%) and 3 (7%). Early changes include spotted consolidation in the majority and ground glass opacity in about 40% of patients within the first six months. Partial atelectasis or pleural effusion were observed in 10-20%, respectively. In the period after 6 months, streaky or dense consolidation were noted in the majority of follow-up images. The lung tissue consolidation progresses into retraction. Lung atelectasis occurred in about 10% of patients. Pleural effusion was noted more rarely. CONCLUSION: As a result of high focal doses in one fraction, tissue consolidation must be expected in all patients, with progressive retraction predominantly in the second year after brachytherapy. There is a smaller risk of partial atelectasis and pleural effusion.