Funding for this research was provided by:
Varian Medical Systems
Received: 20 May 2020
Accepted: 19 August 2020
First Online: 27 August 2020
Ethics approval and consent to participate
: When appropriate, the ethics committees at the participating institutions approved this project. Given that this was a retrospective study of anonymized patient records, such approval was not required at some centres.
: Not applicable.
: The authors declare that they have no competing interests.
: No actual or potential conflicts of interest exist.The study was supported by grant from Varian Medical Systems.This project was approved by the ethics committees at the participating institutions.