Findings
In this randomized clinical trial of 330 patients aged 70 years and older with EC who were randomly assigned to receive SIB-RT with concurrent and consolidated oral S-1 chemotherapy (CRTCT) or SIB-RT alone, 3-year overall survival and progression-free survival of participants in the CRTCT group were superior to that of SIB-RT group. The incidence of grade 3 to 5 toxic effects was similar in both groups.