Surface-based deep inspiration breath-hold radiotherapy in left-sided breast cancer: final results from the SAVE-HEART study

Background: Adjuvant radiotherapy (RT) plays an essential role in the management of early breast cancer (BC), but can lead to cardiovascular and lung toxicities. RT in deep inspiration breath hold (DIBH) often allows better protection of organs at risk. This prospective study compares surface-guided DIBH with free breathing (FB) in patients with left-sided BC, by evaluating individual cardiovascular risks and treatment plan dosimetry. Patients and methods: The study enrolled 585 patients from October 2016 to January 2021 with left-sided invasive breast carcinoma with indicated adjuvant RT of the breast/thoracic wall with or without regional lymph nodes. The ability to hold breath for 20 s was a prerequisite. The treatments were either hypofractionated (HF; 40.05 Gy/15Fx) or normofractionated (NF; 50.00 Gy/25Fx). DIBH was applied using the automatically triggered surface guidance system Catalyst with audio-video feedback. Computed tomography and surface data were acquired during both DIBH and FB. The primary endpoint of the study was the comparative evaluation of heart dose reduction using DIBH. Results: Plan dosimetry was significantly improved by DIBH. The mean and maximum doses to the heart and the left coronary artery were significantly reduced by 36%-42% in HF and NF plans (P < 0.001), while the mean ipsilateral lung dose was reduced by 12%-14% (P < 0.001). Furthermore, DIBH resulted in a 5% reduction in the cumulative 10-year cardiovascular disease risk (10-year cardiovascular disease risk) compared with FB (3.59% to 3.41%; P < 0.001). Conclusion: To the best of our knowledge, this is the largest prospective study showing better sparing for cardiac and ipsilateral lung doses with surface-guided DIBH compared with FB in patients with left-sided BC.