Voluntary Inspiration Breath-hold Technique in Left-sided Breast Cancer Radiation Therapy in Asian

Abstract

Purpose or Objective: Radiation treatment to the left breast is associated with increased cardiac morbidity and mortality. This study aims to evaluate the reduction of cardiac radiation dose with voluntary inspiration breath-hold (VIBH) technique compared to free breathing (FB) in patients with leftsided breast cancer. It also aims to identify predictors of patients who are associated with more benefit with VIBH. Material and Methods: Twenty-six patients with left-sided breast cancer (22 post-breast conservative surgery (BCT) and 4 postmastectomy(M)) underwent VIBH and FB planning computed tomography scans, and the 2 plans were compared. Cardiac shields were used in the post- BCT plans if necessary, provided that clinical treatment volume coverage was not compromised, while chest wall coverage took priority in post-M plans. The singleisocenter conformal fields in the field treatment plans were generated with the Eclipse Treatment Planning System (Varian Medical Systems) for both FB and DIBH images. The prescribed dose was 40Gy in 15 fractions for the whole breast or the chest wall. Dose volume histogram parameters for heart, lung and optimized planning target volume (OPTV) were compared between VIBH and FB. The impact of VIBH was compared in post-BCS and post-M patients using Wilcoxon signed rank test. Results: Dose conformity and PTV coverage were similar with VIBH and FB. When compared with FB, VIBH resulted in a significant reduction of mean cardiac dose from 3.18+/- 1.51 to 1.61+/-0.63Gy (p<0.0001). The relative heart volume irradiated with 20Gy-40Gy was consistently reduced. 71% patients had an absolute reduction of mean heart dose by 1Gy with VIBH. VIBH decreased the mean heart dose by 2.62Gy (3.88 vs. 1.26Gy; p=0.03) in post-M group, and 1.38Gy (3.06 vs. 1.68Gy; p<0.0001) in post-BCT group. Differences between FB and VIBH-derived lung V18Gy (19.67 vs. 20.69Gy, p=0.83) were non-significant. On multivariate analysis, age, body weight and use of chemotherapy were not associated with differences in mean heart dose. Conclusion: VIBH demonstrated significant reduction of cardiac doses without compromising the target volume coverage. Differences in lung doses were non-significant. Although VIBH provides a better treatment outcome with lower cardiac dose compared with FB, VIBH is more time consuming and requires patient's cooperation. In centres where VIBH availability is limited, VIBH is more preferably used in post-M patients than post-BCT patients as cardiac shields are more readily applicable in post-BCT patients.