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Purpose: This retrospective planning study aimed to verify the usefulness of a clinically available method, dynamic swing arc (DSA), a noncoplanar volumetric modulated arc therapy (VMAT) technique, of the new accelerator OXRAY for head and neck squamous cell carcinoma (HNSCC). We performed dosimetric comparisons between DSA and conventional coplanar/noncoplanar VMAT (C-VMAT/NC-VMAT) plans for HNSCC. Methods and Materials: We selected 32 patients with oropharyngeal and hypopharyngeal cancer treated with C-VMAT at National Cancer Center Hospital East between September 2018 and July 2023. DSA and C/NC-VMAT plans were generated using OXRAY and TrueBeam, respectively. DSA employed noncoplanar 2-arc beams with an O-ring gantry swing, whereas C-VMAT and NC-VMAT used coplanar and noncoplanar 2-arc beams, respectively. Dosimetric parameters, normal tissue complication probability, and delivery times were compared pairwise using the Wilcoxon signed-rank test with Bonferroni correction. Results: For high-risk planning target volume (PTV), D98 values in NC-VMAT plans were closest to the prescribed dose, significantly differing from C-VMAT and DSA plans. DSA plans showed significantly better median conformity and homogeneity indices (0.97 and 7.33, respectively) compared to C-VMAT (0.95 and 8.36) and NC-VMAT (0.96 and 7.96) plans. DSA plans significantly reduced the mean ipsilateral/contralateral parotid gland dose by 5.78/6.93 and 2.88/1.56 Gy (median) compared to C-VMAT and NC-VMAT. NC-VMAT and DSA plans significantly decreased the mean oral cavity dose by 2.16 and 3.22 Gy (median) compared to C-VMAT. DSA plans had the lowest median normal tissue complication for xerostomia with significant differences, followed by NC-VMAT and C-VMAT. The delivery time for DSA plans was longer than VMAT (151 seconds vs 124 seconds), but shorter than NC-VMAT. Conclusions: DSA plans using OXRAY for HNSCC maintained PTV coverage while reducing parotid gland and oral cavity mean doses compared to coplanar VMAT plans, although delivery times increased. DSA plans reduced parotid gland doses and delivery times compared to noncoplanar VMAT plans.

Abstract Background Volumetric modulated arc therapy (VMAT) for locally advanced rectal cancer (LARC) has emerged as a promising technique, but the planning process can be time-consuming and dependent on planner expertise. We aimed to develop a fully automated VMAT planning program for LARC and evaluate its feasibility and efficiency. Methods A total of 26 LARC patients who received VMAT treatment and the computed tomography (CT) scans were included in this study. Clinical target volumes and organs at risk were contoured by radiation oncologists. The automatic planning program, developed within the Raystation treatment planning system, used scripting capabilities and a Python environment to automate the entire planning process. The automated VMAT plan (auto-VMAT) was created by our automated planning program with the 26 CT scans used in the manual VMAT plan (manual-VMAT) and their regions of interests. Dosimetric parameters and time efficiency were compared between the auto-VMAT and the manual-VMAT created by experienced planners. All results were analyzed using the Wilcoxon signed-rank sum test. Results The auto-VMAT achieved comparable coverage of the target volume while demonstrating improved dose conformity and uniformity compared with the manual-VMAT. V30 and V40 in the small bowel were significantly lower in the auto-VMAT compared with those in the manual-VMAT (p