Voluntary deep inspiration breath-hold reduces the heart dose without compromising the target volume coverage during radiotherapy for left-sided breast cancer

Abstract

Abstract

Background and aim: During radiotherapy of left-sided breast cancer, parts of the heart are irradiated, which may lead to late toxicity. We report on our experience with cardiac-sparing radiotherapy using voluntary deep inspiration breath hold (V-DIBH) and compare its dosimetric outcome with free breathing (FB) technique.

Materials and Methods:  Left-sided breast cancer patients, treated at our department with postoperative radiotherapy between May 2015 and January 2017, were considered for inclusion. FB-computed tomography (CT) was obtained and dose-planning performed. Cases with cardiac V25Gy ≥ 5% or risk factors for heart disease were coached for V-DIBH. Compliant patients were included. They underwent additional CT in V-DIBH for planning, followed by V-DIBH radiotherapy. Dose volume histogram parameters for heart, lung and optimized planning target volume (OPTV) were compared between FB and BH. Treatment setup shifts and systematic and random errors for V-DIBH technique were compared with FB historic control.

Results: Sixty-three patients were considered for V-DIBH. Nine (14.3 %) were non-compliant at coaching, leaving 54 cases for analysis. When compared with FB, V-DIBH resulted in a significant reduction of mean cardiac dose from 6.0 +/- 2.1 to 3.0 +/- 1.1 Gy (p<0.001), maximum cardiac dose from 51.4 +/- 2.0 to 49.1 +/- 5.6 Gy (p=0.005) and cardiac V25Gy from 8.8 +/- 4.2 to 3.1 +/- 2.2 % (p<0.001). Heart volumes receiving low (10 – 20 Gy) and high (30 – 50 Gy) doses were also significantly reduced. Differences between FB- and V-DIBH-derived mean lung dose (9.5 +/- 2.0 vs. 9.5 +/- 2.0 Gy), lung V20Gy (16.8 +/- 4.2 vs. 14.7 +/- 4.9 Gy) and V95% for the OPTV (95.6 +/- 4.1 vs. 95.2 +/- 6.3 %) were non-significant. V-DIBH-derived mean shifts for initial patient setup were ≤ 2.7 mm. Random and systematic errors were ≤ 2.1 mm. These results did not differ significantly from historic FB controls.

Conclusion: When compared with FB, V-DIBH demonstrated high setup accuracy and enabled significant reduction of cardiac doses without compromising the target volume coverage. Differences in lung doses were non-significant.