Exhibit Hall | Forum 7
Purpose: The first clinical biology-guided radiation therapy (BgRT) system – RefleXion™ X1 - was installed and commissioned for clinical use at our institution. This study aimed at evaluating the treatment plan quality and delivery efficiency for IMRT/SBRT cases without PET-guidance.
Methods: Forty-two patient plans across six cancer sites (conventionally-fractionated lung, head and neck, anus, prostate, brain, and lung SBRT) planned with the Eclipse™ treatment planning system (TPS) and treated with either a TrueBeam® or Trilogy® were selected for this retrospective study. For each Eclipse VMAT plan, two corresponding plans were generated on the X1 TPS with 10 mm jaws (X1-10mm) and 20 mm jaws (X1-20mm) using our institutional planning constraints. All clinically relevant metrics in this study, including PTV D95%, PTV D2%, Conformity Index (CI), R50, organs-at-risk (OAR) constraints, and beam-on time were analyzed and compared between 126 VMAT and RefleXion plans using paired t-tests.
Results: All but three planning metrics were either equivalent or superior for the 15 X1-10mm plans as compared to the Eclipse VMAT plans across all planning sites investigated. The Eclipse VMAT and X1-10mm plans generally achieved superior plan quality and sharper dose fall-off superior/inferior to targets as compared to the X1-20mm plans, however, the X1-20mm plans were still considered acceptable for treatment. Strong correlation was observed between the TPS-calculated beam-on time and PTV length in the superior-inferior direction for the X1-10mm (R2 = 0.87) and X1-20mm (R2 = 0.85) plans. On average, the required beam-on time increased by a factor of 1.6 across all sites for X1-10mm compared to X1-20mm plans.
Conclusion: Clinically acceptable IMRT/SBRT treatment plans were generated with the X1 TPS for both the 10 mm and 20 mm jaw settings. The X1-10mm plans were equivalent or superior to the Eclipse VMAT plans, however the beam-on times were longer.