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Gross tumour volume (GTV) delineation on magnetic resonance imaging (MRI), for stage III lung cancer: consensus recommendations needed to ensure contouring consistency
Shiarli, A. Brown, S. Dubec, Michael Bainbridge, H. Koh, D. Lalezari, F. van Herk, Marcel Wetscherek, A. Knowles, E. Faivre-Finn, Corinne
Shiarli, A.
Brown, S.
Dubec, Michael
Bainbridge, H.
Koh, D.
Lalezari, F.
van Herk, Marcel
Wetscherek, A.
Knowles, E.
Faivre-Finn, Corinne
Citations
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Abstract
Introduction: MRI in the context of the radiotherapy (RT) planning
workflow for locally advanced lung cancer (LALC) presents a number
of advantages. MRI provides better soft tissue definition potentially
reducing inter-observer contouring variability of GTV, allowing
tighter margins. This could facilitate the development of intensified
adaptive strategies. Defining the GTV on MRI in lung cancer is novel.
Prior to inter-observer variability assessment, training of clinicians
is paramount.
Methods: Two training workshops were organised. The first
workshop was web-based, led by an MRI radiologist. Fifteen radiation
oncologists participated, from 9 centres internationally. Eight LALC
cases were chosen to cover various anatomical scenarios including
chest wall and mediastinal invasion, and superior sulcus tumours.
The second workshop was face-to-face. The most challenging cases
from the web-based workshop were reviewed, this time with
applied contours checked by the same MRI radiologist. Subsequently,
10 radiation oncologists delineated the GTV on 3 separate cases.
Delineation was performed on T1-weighted mid-position 4D radial
VIBE MRI, registered with the mid-position 4DCT, PET CT and MRI
sequences, including T2 TSE and TSE DIXON. These contours were
compared with those produced by an MRI radiologist.
Results: There are discrepancies in GTV delineation between MRI
radiologists and radiation oncologists, particularly at sites of tumour
invasion causing pleural reaction or bone oedema (Fig. 1). This
demonstrates that recommendations for MRI GTV delineation must
be developed collaboratively between both disciplines. Further
work will involve contouring of 9 LALC cases on MRI, by a 'pair' of an
MRI radiologist and a radiation oncologist from at least 8
international centres. These will be compared against blinded CT/
PET-CT contouring, and discussed, to produce recommendations for
GTV delineation on MRI.
Conclusion: Although GTV contouring on MRI is challenging it
may provide better contrast information compared to CT. Novel MRI-guided adaptive strategies must be optimised collaboratively
between MRI radiologists and radiation oncologists.
Description
Date
2019
Publisher
Collections
Keywords
Type
Meetings and Proceedings
Citation
Shiarli A, Brown S, Dubec M, Bainbridge H, Koh D, Lalezari F, et al. Gross tumour volume (GTV) delineation on magnetic resonance imaging (MRI), for stage III lung cancer: consensus recommendations needed to ensure contouring consistency. Lung Cancer. 2019;127:S77-S.