“…Prospective review of target volume delineation and treatment plans, within and outside the context of clinical trials, is considered best practice to reduce the risk of systematic errors and support ongoing improvement [4,8,26e29]. Unfortunately, uneven distribution of expertise and resources extends to the provision of RTQA initiatives [8,9], which have demonstrated an ability to mitigate planning errors [21e23]. As an independent, centralised platform, QUARTET provides the expertise, infrastructure, and funding for RTQA activities so that it is not dependent on, nor borne by, national providers.…”