Improving radiotherapy quality assurance in clinical trials: assessment of target volume delineation of the pre-accrual benchmark case.

As the complexity of radiotherapy (RT) trials increases, issues surrounding target volume delineation will become more important. Some form of outlining assessment prior to trial entry is increasingly being mandated in UK RT trials. This document produced by the Outlining and Imaging Subgroup (OISG) of the National Cancer Research Institute will address methods to reduce interobserver variation in clinical trials and how to conduct an assessment of outlining through a pre-accrual benchmark case. We review currently available methods of describing the variation and identify areas where further work is needed. The OISG would encourage ongoing discussion with chief investigators in order to provide advice on individual aspects of benchmark case assessment for current and future trials.