Abstract
BackgroundTo improve split-VMAT technique by optimizing treatment delivery time for deep-inspiration breath hold (DIBH) radiotherapy in left-sided breast cancer patients, when automatic beam-interruption devices are not available.MethodsTen consecutive patients were treated with an eight partial arcs (8paVMAT) plan, standard of care in our center. A four partial arcs (4paVMAT) plan was also created and actual LINAC outputs were measured, to evaluate whether there was a dosimetric difference between both techniques and potential impact on the delivered dose. Subsequently, ten other patients were consecutively treated with a 4paVMAT plan to compare the actual treatment delivery time between both techniques. The prescribed dose was 40.05 Gy/15 fractions on the PTV breast (breast or thoracic wall), lymph nodes (LN) and intramammary lymph node chain (IMN). Treatment delivery time, PTVs coverage, conformity index (CI), organs at risk (OAR) dose, monitor units (MU), and gamma index were compared.ResultsBoth split-VMAT techniques resulted in similar dose coverage for the PTV Breast and LN, and similar CI. For PTV IMN we observed a 5% increased coverage for the volume receiving ≥ 36 Gy with 4paVMAT, with an identical volume receiving ≥ 32 Gy. There was no difference for the OAR sparing, with the exception of the contralateral organs: there was a 0.6 Gy decrease for contralateral breast mean (p ≤ 0.01) and 1% decrease for the volume of right lung receiving ≥ 5 Gy (p = 0.024). Overall, these results indicate a modest clinical benefit of using 4paVMAT in comparison to 8paVMAT. An increase in the number of MU per arc was observed for the 4paVMAT technique, as expected, while the total number of MU remained comparable for both techniques. All the plans were measured with the Delta4 phantom and passed the gamma index criteria with no significant differences. Finally, the main difference was seen for the treatment delivery time: there was a significant decrease from 8.9 to 5.4 min for the 4paVMAT plans (p < .05).ConclusionsThis study is mainly of interest for centers who are implementing the DIBH technique without automatic beam-holding devices and who therefore may require to manually switch the beam on and off during breast DIBH treatment. Split-VMAT technique with 4 partial arcs significantly reduces the treatment delivery time compared to 8 partial arcs, without compromising the target coverage and the OAR sparing. The technique decreases the number of breath holds per fraction, resulting in a shorter treatment session.
Highlights
In the last 15 years, considerable efforts have been made to minimize cardiac and lung toxicity of postoperative radiotherapy for left-sided breast cancer
Different treatment planning solutions to combine deep-inspiration breath hold (DIBH) and volumetric modulated arc therapy (VMAT) are described in the literature, including the use of multiple small partial arcs that mimic tangential fields; a full 360° arc; a hybrid plan combining tangential fields and partial arcs; and a single or double partial arc totaling between 190° and 250° [6,7,8,9,10,11,12,13,14]
Treatment planning techniques Two different planning techniques are compared in this study: a 8 partial arcs VMAT (8paVMAT) and a 4 partial arcs VMAT (4paVMAT).In an 8paVMAT plan, 30° overlapping arcs mimic tangential fields, where the start/ stop angle was between 300°/20° for the medial arcs and between 80°/180° for the lateral ones
Summary
In the last 15 years, considerable efforts have been made to minimize cardiac and lung toxicity of postoperative radiotherapy for left-sided breast cancer. When using DIBH techniques, SGRT enables monitoring of the patient movements and respiration, optimizing position reproducibility and minimizing internal target motion, increasing the accuracy of the treatment of specific anatomic sites [19,20,21]. This system can be linked to the treatment machine to trigger automatic beam delivery or beam hold when respiration is within predefined respiratory phases [20]. To improve split-VMAT technique by optimizing treatment delivery time for deep-inspiration breath hold (DIBH) radiotherapy in left-sided breast cancer patients, when automatic beam-interruption devices are not available
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
