1 Division of Radiation Oncology, National Cancer Centre (NCCS), Singapore, Singapore. kevin.chua.l.m@singhealth.com.sg.
2 Division of Radiation Oncology, National Cancer Centre (NCCS), Singapore, Singapore. david.tan.b.h@singhealth.com.sg.
3 Division of Radiation Oncology, National Cancer Centre (NCCS), Singapore, Singapore; Oncology Academic Program, Duke-NUS Graduate Medical School (Duke-NUS), Singapore, Singapore. melvin.chua.l.k@singhealth.com.sg.
4 Department of Radiation Oncology, University of Washington School of Medicine, Seattle, Washington, USA. simonslo@uw.edu.