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Tumour shape features are not the prognostic factors they appear to be
Davey, Angela Mistry, Hitesh McWilliam, Alan
Davey, Angela
Mistry, Hitesh
McWilliam, Alan
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Abstract
Introduction: Tumour shape features have shown promise as
prognostic markers, linking irregular tumour shape with worse
prognosis. This study investigates tumour sphericity as a predictor
of overall survival (OS) in lung cancer patients. Importantly, we
consider the alternative that sphericity is correlated with known
prognostic factors.
Methods: 487 lung cancer patients with a range of histological subtype
were treated with curative-intent radiotherapy (55Gy over 20
fractions). These patients had a single gross tumour volume (GTV)
delineated on planning CT. Sphericity was calculated as the ratio of
the surface area of a sphere with equivalent volume to the GTV, to
the surface area of the GTV. Relationships between sphericity and
common patient and tumour characteristics were investigated. A
multivariate Cox regression was performed to assess sphericity as prognostic for OS. A subset analysis was performed for 300 patients
with N-stage N0 to remove potential influence of nodal involvement
on sphericity.
Results: Sphericity is significantly correlated with known prognostic
factors: tumour volume, mean lung dose, N-stage, and
T-stage. Sphericity is a significant predictor of OS in a univariate
Cox regression, but not significant in multivariate analysis (Table 1).
For N0 subset analysis, sphericity is higher on average (0.648 vs
0.620) and is no longer significant in univariate analysis (p=0.088,
HR=0.267). Conclusion: Sphericity is heavily influenced by the GTV and
correlates with known prognostic factors: volume, stage, and
mean lung dose. This is not considered in many radiomic studies.
In addition, this study emphasises the importance of distinction
between primary tumour and nodes for radiomic analysis. Without
separation, the inclusion of nodes within the GTV will bias analysis,
leading to more irregular shapes for higher N-stage. Issues identified
are likely relevant for other radiomic features. Future work will
investigate independent characteristics descriptive of the tumour
border as oppose to the GTV volume.
Description
Date
2019
Publisher
Collections
Keywords
Type
Meetings and Proceedings
Citation
Davey A, Van Herk M, Faivre-Finn C, Mistry H, McWilliam A. Tumour shape features are not the prognostic factors they appear to be. Lung Cancer. 2019;127:S80-S1.