The Potential Role of Lung Ultrasound B-Lines for Detection of Lung Radio-Induced Toxicity in Breast Cancer Patients after Radiation Therapy

Background and Purpose Breast cancer patients exposed to doses of radiation after radiotherapy could develop toxicity to lung. Lung ultrasound (LUS) is able to detect interstitial lung disease by the evaluation of B-lines. The aim of our study was to assess the number of B-lines to diagnose lung involvement after chest radiotherapy. Materials and Methods We measured LUS B-lines in the treated and contralateral lung of 20 breast cancer patients, 1-3 months after the end of radiotherapy and 1 year after previous LUS. The sum of the B-lines number in the 72 sites on anterior and posterior chest yielded a global B-lines score. Results B-lines were more numerous in treated (median: 21; 1st-3rd quartiles: 11-31) versus untreated hemithorax (median: 3; 1st-3rd quartiles: 1-5) in both examination at T1-3 months (Kolmogorov-Smirnov test P < 0.001) and T1 year (median: 21; 1st-3rd quartiles: 12-28 vs. median: 4; 1st-3rd quartiles: 1-10; Kolmogorov-Smirnov test P < 0.01). Within the treated hemithorax, B-lines were more frequent in the anterior than in the posterior chest in both examination at T1-3 months (Kolmogorov-Smirnov test: P < 0.0001) and T1 year (Kolmogorov-Smirnov test: P < 0.01). Abnormal scores (B-lines>5) were present in 17/20 treated versus 7/20 untreated hemithoraxes (85.0 vs. 35.0%, P < 0.01) in the first LUS and likewise in 16/17 treated versus 7/17 in untreated hemithorax (94.1% vs. 41.2%, P < 0.01) after 1-year follow-up. Conclusion Among women receiving radiotherapy after breast cancer, B-lines are present predominantly in the irradiated lung. These data suggest that B-lines by LUS could provide, at a subclinical stage, a radiation-free biomarker of radiotherapy-induced lung damage.