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. 2017 May;90(1073):20160826.
doi: 10.1259/bjr.20160826. Epub 2017 Mar 24.

The role of delineation education programs for improving interobserver variability in target volume delineation in gastric cancer

Cem Onal  1 , Mustafa Cengiz  2 , Ozan C Guler  1 , Yemliha Dolek  1 , Serdar Ozkok  3
Affiliations

The role of delineation education programs for improving interobserver variability in target volume delineation in gastric cancer

Cem Onal et al. Br J Radiol. 2017 May.

Abstract

Objective: To assess whether delineation courses for radiation oncologists improve interobserver variability in target volume delineation for post-operative gastric cancer radiotherapy planning.

Methods: 29 radiation oncologists delineated target volumes in a gastric cancer patient. An experienced radiation oncologist lectured about delineation based on contouring atlas and delineation recommendations. After the course, the radiation oncologists, blinded to the previous delineation, provided delineation for the same patient.

Results: The difference between delineated volumes and reference volumes for pre- and post-course clinical target volume (CTV) were 19.8% (-42.4 to 70.6%) and 12.3% (-12.0 to 27.3%) (p = 0.26), respectively. The planning target volume (PTV) differences pre- and post-course according to the reference volume were 20.5% (-40.7 to 93.7%) and 13.1% (-10.6 to 29.5%) (p = 0.30), respectively. The concordance volumes between the pre- and post-course CTVs and PTVs were 467.1 ± 89.2 vs 597.7 ± 54.6 cm3 (p < 0.001) and 738.6 ± 135.1 vs 893.2 ± 144.6 cm3 (p < 0.001), respectively. Minimum and maximum observer variations were seen at the cranial part and splenic hilus and at the caudal part of the CTV. The kappa indices compared with the reference contouring at pre- and post-course delineations were 0.68 and 0.82, respectively.

Conclusion: The delineation course improved interobserver variability for gastric cancer. However, impact of target volume changes on toxicity and local control should be evaluated for further studies. Advances in knowledge: This study demonstrated that a delineation course based on current recommendations helped physicians delineate smaller and more homogeneous target volumes. Better target volume delineation allows proper target volume irradiation and preventing unnecessary normal tissue irradiation.

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Figures

Figure 1.
Figure 1.
Pre-operative CT scan demonstrated a thickening of the wall extending from the oesophagogastric junction to the corpus (arrows) with no lymphadenopathy or distant metastasis.
Figure 2.
Figure 2.
A representative image demonstrating planning target volumes (PTVs) delineated by course attendees and the reference (bold line) at (a) transverse, (b) sagittal and (c) coronal sections before the delineation course. (d–f) The PTVs delineated by attendees after the delineation course.
Figure 3.
Figure 3.
The (a) clinical target volumes and (b) planning target volumes delineated before and after the delineation course. The dotted black line indicates the reference volume.
Figure 4.
Figure 4.
The (a) clinical target volume and (b) planning target volume changes before and after the delineation course according to the reference contouring.
Figure 5.
Figure 5.
The target volume delineated by a representative observer (light line) compared with the reference contour (dark line). Moderate variation at the cranial part, portal hilus and splenic hilus (a–c) and maximum variation at the caudal part (d) were observed before the course. An evident improvement was seen at post-course contouring at every borders of target volume (e–h).
See this image and copyright information in PMC

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