3644 - Radiotherapy Planning for Lung Cancer Using Novel Volumetric Modulated Arc Therapy with Static Angle Modulated Ports and Dynamic Collimator Rotation
Presenter(s)
T. Ueda1, Y. Kondo2, N. Hayashi2, S. Komatsu1, T. Ogura1, T. Fujiwara1, and T. Kimura1; 1Department of Radiation Oncology, Kochi Medical School, Kochi University, Kochi, Japan, 2Department of Medical Technology, Kochi Medical School Hospital, kochi, Japan
Purpose/Objective(s): A newly developed treatment planning technique enables automatic optimization of collimator angles according to target shape and incorporation of static angle modulated ports (STAMPs), which permit beam delivery to stop at arbitrary gantry angles during irradiation (VMATp).This study aimed to compare RAD with conventional volumetric modulated arc therapy (VMAT).
Materials/Methods: Ten patients with unresectable locally advanced lung cancer who underwent definitive radiotherapy at our institution between April 2025 and September 2025, were retrospectively planned with conventional VMAT and VMATp. Radiotherapy was generally performed under Real-time Position Management (RPM)-guided breath-hold at quiet inspiration. Prescription dose was D50% = 66 Gy. Conventional VMAT plan used 2 or 3 static collimator arcs, and VMATp plan used the same number of arcs with dynamic collimator and included 2–4 STAMPs per arc. Dosimetric parameters (including Lung-GTV V5 Gy, V20 Gy, Dmean, PTVD98%, D2%) were compared using the Wilcoxon signed-rank test.
Results: In all ten cases, VMATp reduced lung dose while maintaining dose coverage to the PTV. Compared with conventional VMAT, VMATp showed the following results: Lung-GTV V20 Gy (21.0% vs 18.1%, p= 0.005), V5 Gy (48.3% vs 46.1%, p= 0.075), Dmean (11.7 Gy vs 10.7 Gy, p= 0.005), PTV D98% (85.6% vs 85.6%, p= 0.959), and D2% (105.8% vs 106.2%, p= 0.333).
Conclusion: VMATp enabled lung dose reduction compared with conventional VMAT while maintaining target dose coverage. The use of VMATp in lung cancer improved the quality of radiotherapy treatment planning.
Table1: Comparison of dosimetric parameters between conventional VMAT and VMATp plan| parameter | unit | VMAT (mean±SD) | VMATp (mean±SD) | p value |
| Lung-GTV V5 Gy | % | 48.3±10.2 | 46.1±12.9 | 0.075 |
| Lung-GTV V20 Gy | % | 21.0±7.52 | 18.1±6.56 | 0.005 |
| Lung-GTV Dmean | Gy | 11.7±3.14 | 10.7±2.90 | 0.005 |
| PTV D98% | % | 85.6±3.50 | 85.6±2.53 | 0.959 |
| PTV D2% | % | 105.8±3.59 | 106.2±3.43 | 0.333 |