A teaching intervention in a contouring dummy run improved target volume delineation in locally advanced XXXX : Reducing the interobserver variability in multicentre clinical studies.

@entity1 @entity1149 @entity5958
INTRODUCTION: Interobserver variability in the definition of target volumes (TVs) is a well-known confounding factor in (multicentre) clinical studies employing radiotherapy. Therefore, detailed contouring guidelines are provided in the prospective randomised multicentre PET-Plan (NCT00697333) clinical trial protocol. This trial compares strictly FDG-PET-based TV delineation with conventional TV delineation in @entity1 with locally advanced @entity1149 ( @entity1149 ). Despite detailed contouring guidelines, their interpretation by different radiation oncologists can vary considerably, leading to undesirable discrepancies in TV delineation. Considering this, as part of the PET-Plan study quality assurance (QA), a contouring dummy run ( @entity5958 ) consisting of two phases was performed to analyse the interobserver variability before and after teaching. MATERIALS AND METHODS: In the first phase of the @entity5958 ( @entity5958 ), radiation oncologists from 14 study centres were asked to delineate TVs as defined by the study protocol (gross TV, GTV; and two clinical TVs, CTV-A and CTV-B) in a test @entity1 . A teaching session was held at a study group meeting, including a discussion of the results focussing on discordances in comparison to the per-protocol solution. Subsequently, the second phase of the @entity5958 ( @entity5958 ) was performed in order to evaluate the impact of teaching. RESULTS: Teaching after @entity5958 resulted in a reduction of absolute TVs in @entity5958 , as well as in better concordance of TVs. The Overall Kappa(k) indices increased from 0.63 to 0.71 (GTV), 0.60 to 0.65 (CTV-A) and from 0.59 to 0.63 (CTV-B), demonstrating improvements in overall interobserver agreement. CONCLUSION: Contouring DRs and study group meetings as part of QA in multicentre clinical trials help to identify misinterpretations of per-protocol TV delineation. Teaching the correct interpretation of protocol contouring guidelines leads to a reduction in interobserver variability and to more consistent contouring, which should consequently improve the validity of the overall study results.
