Dosimetric comparison of volumetric modulated arc therapy and proton pencil beam scanning with or without deep inspiration breath-hold in left-sided breast cancer irradiation including internal mammary nodes
Journal
Therapeutic Radiology and Oncology
Journal Volume
10
Start Page
Article number 1
ISSN
2616-2768
Date Issued
2026-03
Author(s)
Shen, Eric Yi-Liang
Lin, Chih-Yun
Chang, Fan
Tsai, Tsung-Shiau
Cheng, Ann-Joy
Chang, Joseph Tung-Chieh
Abstract
Background: Left-sided breast cancer radiotherapy poses risks to the heart and lungs due to their proximity to the treatment field. Deep inspiration breath-hold (DIBH) can reduce cardiac exposure by expanding the thoracic cavity, while proton pencil beam scanning (PBS) offers precise dose delivery using the Bragg peak. We aimed to compare the dosimetric impact of combining DIBH with volumetric modulated arc therapy (VMAT) and PBS, focusing on sparing the heart, left anterior descending artery (LAD), lungs, and contralateral breast, especially during internal mammary node (IMN) irradiation. Methods: Ten patients underwent computed tomography (CT) simulation in free breathing (FB) and DIBH states. Four treatment plans were generated: VMAT-FB, VMAT-DIBH, PBS-FB, and PBS-DIBH, prescribing 50.4 Gy in 28 fractions. VMAT used photon beams, while PBS used protons. Dose-volume histogram (DVH) metrics were analyzed for organs at risk (OARs) and targets. Wilcoxon signed-rank tests assessed differences (P<0.05). Results: All techniques achieved acceptable target coverage. PBS significantly reduced cardiac exposure: mean heart dose was 30.52% (VMAT-FB), 26.45% (VMAT-DIBH), 1.87% (Proton-FB), and 0.41% (Proton-DIBH; P<0.01). The LAD mean dose similarly decreased from 60.05% (VMAT-FB) to 45.32% (VMAT-DIBH), to 18.67% (Proton-FB), and to 5.60% (Proton-DIBH; P<0.01). Left lung mean dose was substantially lower with protons: 8.44% (Proton-FB) and 9.53% (Proton-DIBH) compared to 30.06% (VMAT-FB) and 30.22% (VMAT-DIBH). The modest increase with DIBH in proton plans (1.09% absolute) reflects lung expansion during breath-hold. Proton therapy virtually eliminated contralateral breast dose (0.18% Proton-DIBH vs. 12.69% VMAT-DIBH; P<0.01). Conclusions: PBS with DIBH offers the greatest reduction in cardiac and LAD doses, especially in IMN irradiation, while maintaining target coverage. Despite minimal increases in lung dose, PBS-DIBH provides optimal organ sparing, supporting its clinical use to minimize long-term toxicity in left-sided breast cancer radiotherapy.
Publisher
AME Publishing Company
Type
journal article