Implementing the Royal College of radiologists' radiotherapy target volume definition and peer review guidelines : more still to do?

Abstract

Accurate definition of the gross target volume (GTV) and organs at risk (OARs) is one of the most important steps in high-precision radiotherapy. Ironically, this process has also been described as the ‘weakest link’ in the radiotherapy treatment chain. Numerous studies have shown that this process is prone to interobserver variation and human errors, particularly for lung cancer [3e7]. Contouring errors can be minor, caused by the unavoidable difficulty of distinguishing tumour boundaries from adjacent structures, leading to an increased dose to an OARs, or major, caused by a geographical tumour miss, leading to a possible tumour recurrence. Training and well-defined protocols have been found to reduce the interobserver variation, but they do not eliminate the risk of misinterpreting tumour spread in the images, leading to a gross error in target definition. Numerous studies have shown that quality assurance checks by a second expert or multidisciplinary team (MDT; peer review) can identify gross errors in 17e30% of target volume definitions [8,13e15]. In view of these findings, the Royal College of Radiologists followed the lead of other professional bodies [16e18] and issued guidelines in 2017 to establish minimum standards for peer review as part of radiotherapy quality assurance processes in the UK. No studies have been published evaluating peer review practices across centres in the UK and therefore we conducted a survey of practice with the aim to establish practice and derive recommendations based on the results.