Radiotherapy needs level-1 evidence to support its modality. However, most randomized clinical trials in oncology in the US are industry funded and assess systemic therapies alone.1 Without the financial backing of pharmaceutical companies, the majority of studies seeking to establish new standards of care for radiotherapy are conducted through National Cancer Institute (NCI)鈥揻unded cooperative groups. Yet even among cooperative group trials, systemic therapies dominate.2 With fewer radiotherapy trials enrolling, one might expect existing studies to accrue quickly, yet this is not the case. Illustrating this point, among all currently enrolling radiotherapy cooperative group trials activated at least 6 months ago, two-thirds have achieved less than half of expected accruals and 40% have enrolled no more than 25% projected to date. In this Viewpoint, we discuss reasons for accrual difficulties and propose solutions.