Emma Colvill, Jeremy Booth, Simeon Nill, Martin Fast, James Bedford, Uwe Oelfke, Mitsuhiro Nakamura, Per Poulsen, Esben Worm, Rune Hansen, Thomas Ravkilde, Jonas Scherman Rydhög, Tobias Pommer, Per Munck af Rosenschold, Stephanie Lang, Matthias Guckenberger, Christian Groh, Christian Herrmann, Dirk Verellen, Kenneth Poels, Lei Wang, Michael Hadsell, Thilo Sothmann, Oliver Blanck, Paul Keall

• Purpose: A study of real-time adaptive radiotherapy systems was performed to test the hypothesis that, across delivery systems and institutions, the dosimetric accuracy is improved with adaptive treatments over non-adaptive radiotherapy in the presence of patient-measured tumor motion. Methods and materials: Ten institutions with robotic(2), gimbaled(2), MLC(4) or couch tracking(2) used common materials including CT and structure sets, motion traces and planning protocols to create a lung and a prostate plan. For each motion trace, the plan wasPurpose: A study of real-time adaptive radiotherapy systems was performed to test the hypothesis that, across delivery systems and institutions, the dosimetric accuracy is improved with adaptive treatments over non-adaptive radiotherapy in the presence of patient-measured tumor motion. Methods and materials: Ten institutions with robotic(2), gimbaled(2), MLC(4) or couch tracking(2) used common materials including CT and structure sets, motion traces and planning protocols to create a lung and a prostate plan. For each motion trace, the plan was delivered twice to a moving dosimeter; with and without real-time adaptation. Each measurement was compared to a static measurement and the percentage of failed points for gamma-tests recorded. Results: For all lung traces all measurement sets show improved dose accuracy with a mean 2%/2 mm gamma-fail rate of 1.6% with adaptation and 15.2% without adaptation (p < 0.001). For all prostate the mean 2%/2 mm gamma-fail rate was 1.4% with adaptation and 17.3% without adaptation (p < 0.001). The difference between the four systems was small with an average 2%/2 mm gamma-fail rate of <3% for all systems with adaptation for lung and prostate. Conclusions: The investigated systems all accounted for realistic tumor motion accurately and performed to a similar high standard, with real-time adaptation significantly outperforming non-adaptive delivery methods.…