[1] NUS, Natl Canc Ctr Singapore, Div Clin Trial & Epidemiol Sci, 11 Hosp Dr, Singapore 169610, Singapore
[2] NUS, Yong Loo Lin Sch Med, Saw Swee Hock Sch Publ Hlth, Singapore, Singapore
[3] NUS, Natl Canc Ctr Singapore, Dept Radiat Oncol, Singapore, Singapore
[4] Duke NUS Grad Med Sch Singapore, Med Educ Res & Evaluat Dept MERE, Singapore, Singapore