Evaluation Of Photon And Proton Radiotherapy Plan Quality With The Knowledge-Based Approach In Nrg Bn001 Clinical Trial

IMRT is a well-established and mature modality. In comparison, proton therapy is an evolving modality, with an anticipated learning curve that has likely not peaked yet. With this background, we hypothesized that proton plans would demonstrate temporal evolution. We, therefore, used knowledge-based planning models as a radiotherapy quality assurance (RTQA) tool to investigate the changes in the treatment plans quality for photon and proton irradiation over time, for newly diagnosed glioblastoma as part of a multi-institutional clinical trial. 207 treatment plans (enrolled from 2015-19) submitted to NRG (BN001 randomized phase II trial) were used for this study. Of these cases, 139 were from Arm B (photon) and 68 from Arm C (proton). These cases were initially reviewed by the Imaging and Radiation Oncology Core (IROC) RTQA center, and each plan was scored using the dose constraints defined in protocol. We selected some plans that were scored as Per-protocol to generate the knowledge-based plan models (KBP) in Treatment Planning System (TPS), for each Arm, respectively. All plans were then re-optimized by using the applicable model. Finally, we grouped all the plans by modalities (photon or proton) by year; and calculated the average dose-volume parameters for each structure and the difference between these parameters between the original plan and re-optimized plan for each year. For photon group, the average dose-volume parameters for target structures remained stable over the four-year period, and the re-optimized treatment plans did not differ when compared with the original plans for all the average dose-volume parameters (Plan1: submitted plan, Plan2: reoptimized). For proton group, the average dose-volume parameters from 2015 to 2019 did not show a clear trend. However, the OAR dose evaluation in proton plans re-optimized using the KBP model showed a statistically significant difference from the original plan. (Plan1: submitted plan, Plan2: reoptimized). For the photon plans, the quality of the submitted plans was very close to the re-optimized plans with guidance using the KBP model, showing the maturity of the photon IMRT technique. For the proton plans, the re-optimized plan guided by the KBP model showed statistically significant improvement in quality, reducing the OARs doses, while maintaining a sufficient target coverage, demonstrating the evolving opportunity for further quality improvement in proton treatment planning.Tabled 1Abstract 2777; Table 1Arm BPTV_7500 D95% [Gy]BrainStemCore D0.03 cc [Gy]OptChiasm_PRV D0.03 cc [Gy]Plan1Plan2Plan1Plan2Plan1Plan2201573.873.847.344.141.237.5201674.373.946.245.440.236.4201774.674.749.550.731.328.820187574.444.741.336.233.3 Open table in a new tab Tabled 1Abstract 2777; Table 2Arm CPTV_7500 D95% [Gy]BrainStemCore D0.03 cc [Gy]OptChiasm_PRV D0.03 cc [Gy]Plan1Plan2Plan1Plan2Plan1Plan2201574.474.837.830.529.623.2201673.875.235.416.324.213.4201773.474.144.832.234.826.7201874.374.948.138.145.430.7 Open table in a new tab