COVID-19(14) Patient(8) Result(7) Treatment(7) radiation therapy(7) material(7) coronavirus disease(6) clinical trial(6) Radiation(5) clinical(5) lung(5) Pneumonia(5) outcome(4) patients with COVID-19(4) survival(4) low-dose(4) group(3) assessment(3) hospital(3) Trial(3) hazard ratio(3) prevention(3) database(3) COVID-19 pandemic(3) Against(3) resource(3) Follow-up(3) approach(3) 95% confidence interval(3) changes in(3)