Received: 26 June 2020
Accepted: 29 October 2020
First Online: 7 November 2020
Ethics approval and consent to participate
: This study protocol was reviewed and approved by the institutional review board of University of Pennsylvania (Reference No.: 831888).
: All data were stored in the hospital database and extracted for research. The participants’ informed consent requirement was waived due to the retrospective nature of this study.
: NT is on an advisory board for Varian Medical Systems. LD owns a patent with Varian Medical Systems unrelated to this work. JM is a consultant for Varian Medical Systems. TL has received research grants from Varian Medical Systems unrelated to this work.