Stefan Elbers

56 Chapter 2 which the intervention is expected to benefit the patient. Finally, we believe that regular updates of this review may support the critical monitoring of future developments of IMPT programmes, the possibility to correct for data extraction errors and the comparison of different treatment approaches. A living systematic review approach provides the potential to accommodate this. Acknowledgments We greatly appreciate the help that we received from Myrthe Konijnenburg with the data extraction and the expertise of Dr. Marc Teunis, Julien Groenenboom, Mees Fröberg, and Britte Heijink for during the development and deployment of the online multimedia appendix. Author Contributions SE, UK, HWand RS conceived of the presented idea. JK and SE developed the search strategy. SE, SK, UK and JP screened the studies and extracted the data. HW and RS supervised the study. SE and SK developed the online multimedia appendix. All authors discussed the results and contributed to the final version of the manuscript.