International Journal of Radiation Oncology*Biology*Physics
Clinical InvestigationProspective Randomized Double-Blind Pilot Study of Site-Specific Consensus Atlas Implementation for Rectal Cancer Target Volume Delineation in the Cooperative Group Setting
Introduction
Interobserver differences in target volume delineation are a demonstrated source of potential treatment variability in the context of clinical trials that incorporate conformal radiotherapy (RT) approaches 1, 2. Recent publications have suggested that target delineation consensus documentation is highly desirable for clinical trials (3) and that specific instructional or educational interventions might afford a measurable effect in terms of physician contouring 4, 5.
As a part of efforts to improve RT implementation for the Southwest Oncology Group (SWOG) trials and consistent with its focus on quality improvement in cooperative studies, the SWOG Radiation Oncology Committee authorized the present study as a pilot project to achieve the following primary specific aims: the feasibility of centralized target volume delineation evaluation as a pretrial adjunct to a SWOG-sponsored study (SWOG S0713), and the determination of the effect of implementation of a consensus anatomic atlas on target volume variability.
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Methods and Materials
This prospective institutional review board-exempt study was conducted under the auspices of the University of Texas Health Science Center at San Antonio institutional review board. The present study was designed as a double-blind, randomized hypothesis-generating pilot study (Fig. 1). Statistical power for agreement analysis was estimated for a non–Bonferroni-corrected paired-measures Wilcoxon test (assuming a minimum asymptotic relative efficiency of ≥0.863 compared with a paired t test),
Results
Eight SWOG institutions had at least one user submitting contours, as well as a single non–SWOG-affiliated participant. Of the 26 observers directly asked to participate, 15 submitted contour set pairs, of which 14 were technically evaluable (1 expert, 7 in Group A, and 6 in Group B). The nonevaluable contour set consisted of nonconnected, nonoverlapping contours that precluded ready analysis with the cohort at large. The survey results were pooled and tabulated (Table 2).
All 14 remaining
Discussion
Despite the well-known consequences of geometric inaccuracy in target volume delineation 15, 16, 17, interobserver variability in target definition has been demonstrated in a host of studies and at various anatomic sites (18). Simply put, “interobserver variability in the definition of GTV and CTV is a major—for some tumor locations probably the largest—factor contributing to the global uncertainty in radiation treatment planning” (18). Consequently, efforts to implement solutions to possible
Conclusion
The addition of a visual atlas and consensus treatment guidelines to a written protocol increased CTV delineation conformance with the expert-derived contours and increased contour agreement among the participants for the CTVA, but not the GTV or CTVB, for the included rectal cancer case. The detected interobserver (both with and without the atlas) and intraobserver variation in contouring target structures was substantial. Visual atlas-based supplementary target volume specification materials
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Cited by (0)
C. D. Fuller was supported by a training grant from the National Institutes of Health/National Institute of Biomedical Imaging and Bioengineering, “Multidisciplinary Training Program in Human Imaging” (Grant 5T32EB000817-04), a Technology Transfer Grant from the European Society for Therapeutic Radiology and Oncology, and the Product Support Development Grant from the Society for Imaging Informatics in Medicine.
The funders played no role in the study design, collection, analysis, interpretation of data, manuscript writing, or decision to submit the report for publication.
Conflict of interest: none.
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C.D.F. and J.N. contributed equally to this work.