Abstract PS15-07: Deep inspiration breath-hold in right-sided breast irradiation: Quantifying the benefit
Authors: Krishnamurthy Revathy , Lee Grace , Liu Zhihui (Amy) , Pittman Tyler , Fyles Anthony , Koch Christine Anne 
Published: February 2021

Abstract
Background: Deep inspiration breath-hold (DIBH) in left-sided breast radiation therapy (RT) is proven to reduce ipsilateral lung and heart doses. The potential benefit of this technique in right-sided breast RT has not been fully explored. We describe the differences in organs at risk (OAR) dosimetry between DIBH and free-breathing (FB) plans in 15 patients who received right-sided breast RT.
Materials and methods: Fifteen consecutive patients with right-sided breast cancer who received RT with DIBH between January 1, 2016 and August 31, 2019 were enrolled in this study. All patients initially underwent RT planning with FB scans, and subsequently required DIBH rescanning due to concerns related to exposure of OAR. Dose volume histograms (DVH) for the target volume and OAR coverage were compared between both plans on RayStation Treatment Planning System to quantify the benefit of DIBH. The median value of relative reduction (MRR) and interquartile range in dosimetric parameters were calculated when comparing DIBH to FB. Two-sided Wilcoxon signed-rank test was performed, and a p-value &lt; 0.05 was considered statistically significant.
Results: The median age of patients was 64 (38-78). None of the patients had cardiac, respiratory or hepatic comorbidities. The majority of patients (10/15) received locoregional RT (50 Gy in 25 fractions); the remaining 5 patients received breast RT (42.4 Gy in 16 fractions). Tumor bed boost was delivered in 9 of 15 patients. DIBH was delivered throughout RT to 14/15 patients and the clinical goal(s) for which DIBH was introduced was achieved in all cases. DIBH was most commonly used to minimize liver exposure (11/15 patients); in 3 of these 11 patients, reduction in heart or lung exposure was also required. Statistically significant reductions in the imaged liver V5Gy [MRR 89.8% (99 to 71.6, p&lt;0.001)], V10Gy [MRR 94.7% (100 to 77.9, p&lt;0.001)], V20Gy [MRR 97.2% (100 to 84.7, p&lt;0.001)], maximum dose [MRR 15.5% (73.2 to 8, p&lt;0.001)] and average dose [MRR 68.7% (79.4 to 58.6, p&lt;0.001)] were observed with DIBH. Compared to FB, the use of DIBH led to statistically significant reductions in right lung V20 [Median Relative Reduction 20.8% (27.1 to 15.9, p&lt;0.001)], as well as the maximum dose received by the heart and left lung. The target volume coverage was not compromised by DIBH, with at least 99% of the target volume receiving 95% dose in all 15 cases.
Conclusion: DIBH for right-sided breast irradiation effectively reduces exposure to liver, lung and heart while maintaining target volume coverage. It can be employed to achieve specific dosimetric goals in the clinical setting.
Citation Format: Revathy Krishnamurthy, Grace Lee, Zhihui (Amy) Liu, Tyler Pittman, Anthony Fyles, Christine Anne Koch. Deep inspiration breath-hold in right-sided breast irradiation: Quantifying the benefit [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS15-07.