PURPOSE: Randomized controlled trials (RCTs) are the cornerstone of delivering sustained improvements in cancer outcome. To inform radiation therapy research policy and prioritization, we analyze the radiation therapy RCT landscape including comparison with trials of systemic therapies over the same period, with a specific focus on funding and disparities across income settings. METHODS AND MATERIALS: This retrospective cohort study identified all phase 3 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 radiation therapy 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 radiation therapy RCTs (9%) compared with 601 systemic therapy RCTs (87%). Among all radiation therapy RCTs, 47% of them focused on 2 areas of evaluation: (1) combining radiation therapy with systemic agents (25%) and (2) changes in dose fractionation (22%). The most common cancers studied were head and neck (22%), lung (22%), and breast (14%), with cervical cancer trials representing only 3% of the cohort. Among the radiation therapy RCTs, 33% of them met their primary endpoint, and 62% assessed interventions in the curative setting compared with 31% in systemic therapy RCTs. For their country locations, 77% of radiation therapy RCTs took place in high-income countries, 13% in low-and-middle-income countries, and 11% in both high-income and low-and-middle-income countries. For funding, 17% of radiation therapy RCTs received funding from industry compared with 79% of systemic therapy RCTs. CONCLUSIONS: This study highlights the need for greater investment in radiation therapy RCTs and the need to look at the disparities in conducting RCTs globally. The study emphases the urgent need for more capacity building for cancer clinical trials in low-and-middle-income countries and more sustainable funding sources.