Cranial organs at risk delineation: heterogenous practices in radiotherapy planning

Guillaume Vogin,Frederic Dhermain,Liza Hettal,Marie-Virginie Claeys,Zsuzsa Bodgal,Delphine Antoni,Guillaume Peyraga,Paul Retif,Ulrike Schick,Clarisse Bartau,Juliette Thariat,Loic Feuvret

doi:10.1186/s13014-021-01756-y

Abstract

BackgroundSegmentation is a crucial step in treatment planning that directly impacts dose distribution and optimization. The aim of this study was to evaluate the inter-individual variability of common cranial organs at risk (OAR) delineation in neurooncology practice.MethodsAnonymized simulation contrast-enhanced CT and MR scans of one patient with a solitary brain metastasis was used for delineation and analysis. Expert professionals from 16 radiotherapy centers involved in brain structures delineation were asked to segment 9 OAR on their own treatment planning system. As reference, two experts in neurooncology, produced a unique consensual contour set according to guidelines. Overlap ratio, Kappa index (KI), volumetric ratio, Commonly Contoured Volume, Supplementary Contoured Volume were evaluated using Artiview™ v 2.8.2—according to occupation, seniority and level of expertise of all participants.ResultsFor the most frequently delineated and largest OAR, the mean KI are often good (0.8 for the parotid and the brainstem); however, for the smaller OAR, KI degrade (0.3 for the optic chiasm, 0.5% for the cochlea), with a significant discrimination (p < 0.01). The radiation oncologists, members of Association des Neuro-Oncologue d’Expression Française society performed better in all indicators compared to non-members (p < 0.01). Our exercise was effective in separating the different participating centers with 3 of the reported indicators (p < 0.01).ConclusionOur study illustrates the heterogeneity in normal structures contouring between professionals. We emphasize the need for cerebral OAR delineation harmonization—that is a major determinant of therapeutic ratio and clinical trials evaluation.

Highlights

Segmentation is a crucial step in treatment planning that directly impacts dose distribution and opti‐ mization
To our knowledge, inter-observer variability of cephalic organs at risk (OAR) delineation has not been formally reported. The aim of this pragmatic study was to evaluate the inter-individual variability of computed tomography (CT)-based cranial OAR delineation in neurologic radiation oncology practice between various centers and professionals dedicated to this task
This was a multicenter study endorsed by GRANOCEF, the Radiation Group of the Association des Neuro-Oncologue d’Expression Française (ANOCEF)

Summary

Introduction

Segmentation is a crucial step in treatment planning that directly impacts dose distribution and opti‐ mization. The aim of this study was to evaluate the inter-individual variability of common cranial organs at risk (OAR) delineation in neurooncology practice. The organs at risk (OAR) of radiotherapy-associated toxicity, including optic nerves, optic chiasm, retinae, lenses, brainstem, pituitary, cochlea and hippocampus, should be (properly) delineated. This step in the treatment planning is performed manually or (semi) automatically and validated by the radiation oncologist on the treatment planning system from reference computed tomography (CT) images of the patient acquired in the treatment position before the initiation of the treatment. Segmentation is one of the most crucial steps in treatment planning as dose distribution and optimization directly depend on the accuracy of delineation—especially with the most advanced techniques. The aim of this pragmatic study was to evaluate the inter-individual variability of CT-based cranial OAR delineation in neurologic radiation oncology practice between various centers and professionals dedicated to this task

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