Breathing adapted radiotherapy of breast cancer:: reduction of cardiac and pulmonary doses using voluntary inspiration breath-hold

Background and purpose: Adjuvant radiotherapy of breast cancer using wide tangential photon fields implies a risk of late cardiac and pulmonary toxicity. This CT-study evaluates the detailed potential dosimetric consequences of applying breathing adapted radiotherapy (BART), and the feasibility of a monitored voluntary breath-hold technique for right-sided as well as for left-sided tumours. Patients and methods: After breast-conserving surgery, 16 patients were CT-scanned in distinct respiratory phases using the varian realtime position management system(TM) for the monitoring of respiratory anterioposterior chest wall excursion. Each patient underwent three scans: during free breathing (FB), voluntary expiration breath-hold (EBH) and voluntary deep inspiration breath-hold (DIBH). For each scan, an optimised treatment plan was designed with conformal tangential fields encompassing the clinical target volume (CTV) of the breast and ipsilateral internal mammary nodes, and an anterior supraclavicular field. Results: Breath-hold was well accepted by the patients, with a median duration of 24 s for both EBH and DIBH. The mean anterioposterior chest wall excursions were 2.5, 2.6 and 4.1 mm during FB, EBH and DIBH, respectively. During EBH, the mean front chest wall position was 2.7 mm posterior to its mid-FB position, and during DIBH 12.6 mm anterior to its mid-FB position. For right-sided tumours, the median ipsilateral relative lung volume receiving >50% of the prescribed CTV dose was 39, 49 and 32% for FB, EBH and DIBH, respectively. For left-sided tumours, the corresponding percentages were 37, 46 and 31%. The median heart volume receiving >50% of the prescription dose was reduced from 8% for FB to 1% for DIBH, and the median left anterior descending coronary artery volume was reduced from 54 to 5%. Conclusions: Irradiated cardiac volumes can consistently be reduced for left-sided breast cancers using DIBH for wide tangential treatment fields. Additionally, substantial dose reductions in the lung are observed for both right- and left-sided tumours. (C) 2004 Elsevier Ireland Ltd. All rights reserved.