METHODS AND MATERIALS: This retrospective cohort study identified all phase three RCTs evaluating anticancer therapies published from 2014 to 2017. RCTs were classified according to anticancer modality and country of origin. Descriptive statistics were used to compare key characteristics of radiotherapy RCT studies according to study design characteristics, tumor types evaluated, types of intervention appraised, treatment intent and main funding sources.

RESULTS: The study cohort included 694 RCTs of which 64 were radiotherapy RCTs (9%) compared to 601 (87%) systemic therapy RCTs. 47% of all radiotherapy RCTs focused on two areas of evaluation; combining radiotherapy with systemic agents (25%) and changes in dose fractionation (22%). The most common cancers studied were head and neck (22%), lung (22%) and breast (14%) with cervical cancer trials only representing 3% of the cohort. 33% of radiotherapy RCTs met their primary end point. 62% of radiotherapy RCTs assessed interventions in the curative setting compared to 31% in systemic therapy RCTs. 77% of the radiotherapy RCTs were performed in high-income countries (HIC), 13% in low-and-middle-income countries (LMIC) and 11% in both HIC and LMICs. 17% of radiotherapy RCTs received funding from industry compared to 79% of systemic therapy RCTs.