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Multicenter Study
. 2009 Mar 1;73(3):944-51.
doi: 10.1016/j.ijrobp.2008.10.034.

Variability of target and normal structure delineation for breast cancer radiotherapy: an RTOG Multi-Institutional and Multiobserver Study

X Allen Li  1 , An Tai, Douglas W Arthur, Thomas A Buchholz, Shannon Macdonald, Lawrence B Marks, Jean M Moran, Lori J Pierce, Rachel Rabinovitch, Alphonse Taghian, Frank Vicini, Wendy Woodward, Julia R White; Radiation Therapy Oncology Group Multi-Institutional and Multiobserver Study
Affiliations
Multicenter Study

Variability of target and normal structure delineation for breast cancer radiotherapy: an RTOG Multi-Institutional and Multiobserver Study

X Allen Li et al. Int J Radiat Oncol Biol Phys. .

Abstract

Purpose: To quantify the multi-institutional and multiobserver variability of target and organ-at-risk (OAR) delineation for breast-cancer radiotherapy (RT) and its dosimetric impact as the first step of a Radiation Therapy Oncology Group effort to establish a breast cancer atlas.

Methods and materials: Nine radiation oncologists specializing in breast RT from eight institutions independently delineated targets (e.g., lumpectomy cavity, boost planning target volume, breast, supraclavicular, axillary and internal mammary nodes, chest wall) and OARs (e.g., heart, lung) on the same CT images of three representative breast cancer patients. Interobserver differences in structure delineation were quantified regarding volume, distance between centers of mass, percent overlap, and average surface distance. Mean, median, and standard deviation for these quantities were calculated for all possible combinations. To assess the impact of these variations on treatment planning, representative dosimetric plans based on observer-specific contours were generated.

Results: Variability in contouring the targets and OARs between the institutions and observers was substantial. Structure overlaps were as low as 10%, and volume variations had standard deviations up to 60%. The large variability was related both to differences in opinion regarding target and OAR boundaries and approach to incorporation of setup uncertainty and dosimetric limitations in target delineation. These interobserver differences result in substantial variations in dosimetric planning for breast RT.

Conclusions: Differences in target and OAR delineation for breast irradiation between institutions/observers appear to be clinically and dosimetrically significant. A systematic consensus is highly desirable, particularly in the era of intensity-modulated and image-guided RT.

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Conflict of interest statement

Conflict of Interest: There is no conflict of interest for all authors.

Figures

Figure 1
Figure 1
The projection contours of lumpectomy cavity, boost PTV, breast volume, and heart in an axial image (top) and those of breast and heart in a coronal plane (bottom) for Case A.
Figure 2
Figure 2
The contours of the internal mammary nodes, the chest wall, the boost PTV and the heart in an axial image (top) and the contours of the supraclavicular and axillary nodes, the chest wall and the boost PTV, and the heart in a coronal image (bottom) for Case B.
Figure 3
Figure 3
The contours of the internal mammary nodes, the lumpectomy cavity, boost PTV, and the breast volume in an axial plane (top) and those of the supraclavicular and axillary nodes, the lumpectomy cavity, boost PTV and the breast volume in a coronal plane (bottom) for Case C.
Fig. 4
Fig. 4
Dose volume histograms based on the plans generated for the breast volumes and the lungs delineated by nine observers for Case A.
Fig. 5
Fig. 5
Dose volume histograms for Case B generated based on the contours from nine observers for the chest wall and the heart (top) and supraclavicular nodes and the lung (bottom).
Fig. 6
Fig. 6
Dose volume histograms generated for Case C for the boost PTVs, the breast volumes and the lungs defined by nine observers.
See this image and copyright information in PMC

References

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