Helical Photon Plans Provide a Fast and Effective Backup for Proton Therapy
Abstract
Purpose
This study aims to compare plan quality between helical photon and IMPT proton delivery platforms across multiple disease sites to evaluate whether helical plans could provide an effective and rapid backup to proton therapy.
Methods
30 photon and proton plans were generated for 10 patients for different treatment sites including craniospinal irradiation (CSI), head and neck, brain, pelvis, pancreas, liver, lung, scalp, and chest wall. Two treatment planning systems were used: RayStation (TPS1) and Precision (TPS2). All helical plans were optimized using identical dosimetric goals by physicians. For helical plans, jaw size (fixed or dynamic), pitch, and modulation factors were kept consistent across both TPS to comparing delivery time for photon plans only.
Results
All plans met clinical target coverage and organ-at-risk (OAR) constraints for plan quality comparison. For CSI, lung, and head-and-neck cases, proton plans achieved better OAR dose sparing for more than 15% than photon plans; all helical photon plans offered rapid calculation (<10 minutes) and treatment delivery (<20 minutes). For prostate, pancreas and liver SIB plans, helical photon and proton plans yielded comparable dosimetric results for bladder, rectum, liver OARs. For scalp and chest wall patients, photon plans outperformed proton plans due to shallower target depths with improved target coverage of 5%. All helical plans were delivered successfully, with an average QA passing rate of 97% using 3%/3 mm criteria. Setup and delivery times for helical photon treatments were consistently under 20 minutes. Photon Plans generated using Precision TPS plans were shorter compared to RayStation for helical photon plans under the same machine settings.
Conclusion
Helical photon plans can provide clinically comparable plan quality for selected disease sites while offering fast planning and delivery times. These results support helical photon therapy as an effective backup to proton therapy in appropriate clinical implementation.