Split-VMAT technique to control the deep inspiration breath hold time for breast cancer radiotherapy

Abstract

Background 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. Methods Ten 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. Results Both 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). Conclusions This 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.

An Innovative VMAT Technique for Left-sided Breast Cancer Patients With Postmastectomy Radiotherapy (PMRT) Evaluated by Ratio of Heart Volume in Tangent Line (RHVTL)

“…However, the DIBH technique has shown a longer beam-on time and treatment time which could lead to uncertainty of treatment delivery. Poeta et al demonstrated the 4 partial arcs split-VMAT plan could signi cantly reduce treatment delivery time from 8.9 mins to 5.4 mins compared to conventional treatment and each partial arc around 30 seconds which similar to our study (average partial arc approximately 27 seconds) [20]. Base on their feedback from treatment delivery, most patients were able to comfortably hold their breath for more than 20s, the feasibility of our technique should be further analyzed.…”

“…Intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) have been increasingly used to improve plan quality for PMRT and shown to achieve better conformity and homogeneity of PTV, but more scattering doses are obtained in critical organs especially for ipsilateral lung and heart [14][15][16][17][18]. While many studies have discussed the bene t of IMRT and VMAT for PMRT, the e ciency of IMRT has been reported to show more monitor units (MUs) and longer delivery time [19,20]. In this study, we have developed unique VMAT and Hybrid VMAT (H-VMAT) techniques that produce more conformal target volume coverage, excellent homogeneity in the planning target volume, and the acceptable dose of organs at risk for the PMRT patients.…”

Evaluation of Hybrid VMAT Advantages and Robustness Considering Setup Errors Using Surface Guided Dose Accumulation for Internal Lymph Mammary Nodes Irradiation of Postmastectomy Radiotherapy

“…For the whole process, an overall analysis from plan design and implementation to prognosis was conducted. Moreover, the deep inspiration breathhold (DIBH) technology can significantly reduce the radiation dose that the heart and lungs are exposed to during breast cancer radiotherapy (34,35). However, the treatment involving free breathing is still the conventional procedure for treating PMRT patients at our center.…”