Dosimetric impact of interobserver variability in MRI-based delineation for cervical cancer brachytherapy

Abstract Purpose and background To study the dosimetric impact of interobserver delineation variability (IODV) in MRI-based cervical cancer brachytherapy. Materials and methods MR images of six patients were distributed to 10 experienced observers worldwide. They were asked to delineate the target v...

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Published in:Radiotherapy and oncology 2013-04, Vol.107 (1), p.13-19
Main Authors: Hellebust, Taran Paulsen, Tanderup, Kari, Lervåg, Christoffer, Fidarova, Elena, Berger, Daniel, Malinen, Eirik, Pötter, Richard, Petrič, Primož
Format: Article
Language:English
Subjects:
Brachytherapy
Brachytherapy - methods
Cervical cancer
Female
Hematology, Oncology and Palliative Medicine
Humans
Interobserver variability
Magnetic Resonance Imaging, Interventional - methods
Observer Variation
Radiotherapy Dosage
Radiotherapy Planning, Computer-Assisted
Radiotherapy, Image-Guided - methods
Tumor Burden
Uncertainty
Uterine Cervical Neoplasms - pathology
Uterine Cervical Neoplasms - radiotherapy
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Summary:Abstract Purpose and background To study the dosimetric impact of interobserver delineation variability (IODV) in MRI-based cervical cancer brachytherapy. Materials and methods MR images of six patients were distributed to 10 experienced observers worldwide. They were asked to delineate the target volumes and the organs at risk (OARs) for each patient. Two types of reference contours were created (Expert Consensus – EC and Simultaneous Truth and Performance Level Estimation – STAPLE). Optimised plans based on both EC- and STAPLE-contours were prepared. These plans were transferred to each of the observer contour sets and the resulting DVH parameters ( D90 and D2cc ) were calculated. For each patient the standard deviation (SD) for the 10 observers was calculated. Results A mean relative SD of 8–10% was found for GTV and High Risk CTV (HR-CTV) D90 analysing one single fraction. For rectum and bladder the mean relative SD for D2cc was 5–8% while sigmoid was at 11%. For the whole treatment the IODV in HR-CTV caused an uncertainty of ±5 Gyα/β=10 (1SD). The corresponding figure for OARs was ±2–3 Gyα/β=3 . The results were not sensitive as to which structure set was used for the optimisation. Conclusions For the target volumes the dosimetric impact of IODV was smallest for the GTV and HR-CTV, while IODV had an even smaller impact on the bladder and rectum.
ISSN:0167-8140
1879-0887
DOI:10.1016/j.radonc.2012.12.017