Discussion
The ability to provide individualised risk–benefit analysis would help to optimise management decisions in potentially resectable oesophageal cancer. Improving prognostication is a step in this direction as prognosis influences treatment decisions made by doctors and patients. Surgery may have an impact on quality of life for up to 12 months post treatment [
28] and patients with a poorer prognosis may not fully benefit from a multimodal approach. Initial imaging studies have suggested that radiomic features may have additive prognostic value [
11,
12,
18,
21]. However, prespecified models have to demonstrate reliable prediction in external datasets without local refitting. Accordingly, studies need to transition to the evaluation of previously proposed predictors and models, rather than continuing to fit new models with many degrees of freedom to new clinical data [
18].
In this prospective multicentre study, we have demonstrated that a multivariate clinicoradiomic prognostic model (ClinRad) incorporating previously identified CT features improved discrimination of 3-year OS compared to TNM staging with an AUC of 0.68 in the test dataset, but offered similar calibration. The Clinical model had similar performance as the ClinRad model with an AUC of 0.66. Both Clinical and ClinRad models retained discriminative capacity between training and testing, though calibration deteriorated, suggesting a distributional mean shift between institutions.
Our findings are concordant with previously published data of Larue et al [
12], where the high-dimensional random forest radiomic model with other features achieved AUCs of 0.69 and 0.61 in training and testing, respectively. The direction of radiomic coefficients fitted in this study is consistent with previously published results by Zhang et al [
21], who observed increasing GLCM_Correlation in patients with oesophageal adenocarcinoma who responded to chemoradiotherapy. In our model, low GLCM_Correlation was an adverse prognosticator. Our finding that GLCM correlation was the most informative predictor also concurs with Klaasen et al [
22]. However, as Klaasen’s model employed a random forest architecture, the directional concordance of results could not be verified.
Zhang et al [
21] also observed decreasing GLCM contrast in chemoradiotherapy responders. In our study, GLCM contrast did not affect model predictions substantially, indicating that any prognostic information it encoded was already provided by the other clinical and image-based predictors already modelled.
An advantage of our study is that it incorporated multicentre prospective data, thereby providing realistic conditions for the estimation of model informativeness and generalisability. The imaging equipment and protocols were representative of the varying conditions encountered in clinical practice. The imaging acquisition parameters in this dataset reflected typical clinical practice and variations between institutions, which a radiomic model must be able to accommodate. We noted that GLCM correlation and GLCM contrast varied according to institution and scanner manufacturer respectively. This variability introduces noise which can complicate modelling of the underlying prognostic signal. Clinical deployment of radiomic models requires either that this noise is accommodated or that clinical imaging protocols adapt to acquire images under more standard conditions.
Model validation was performed in test data from three institutions which were unobserved during model development, yielding a realistic estimate of model generalisability in our healthcare system. However, our study had limitations. First, manual segmentation especially of early-stage cancers is subject to intra-reader and inter-reader variability [
29]. Second, radiomic approaches are not typically well suited for the identification of new imaging biomarkers, due to the low ratio of events to evaluated variables [
18,
20]. It is noteworthy that the ClinRad model fitted here is simpler than that of Larue, whilst matching its training performance, and marginally improving upon its generalisation [
12]. However, a necessary cost of this study design is that the other informative radiomic features may have been omitted. Third, although both the ClinRad model and TNM staging demonstrated 90% sensitivity, the low specificity achieved at this threshold is a limitation. Fourth, the improvement in performance between the Clinical and ClinRad model is small and unlikely to change clinical management substantially. Finally, the logistic regression models employed in this analysis were insensitive to nonlinear and nonmonotonic effects.
In conclusion, we have confirmed in a prospective multicentre dataset that previously proposed GLCM features—correlation and contrast—contain incremental prognostic information. The clinicoradiomic model incorporating GLCM correlation and contrast with tumour and nodal stage, age and volume outperformed TNM stage alone in the discrimination of 3-year overall survival. Nevertheless, the level of discrimination remained modest and it is questioned if this will impact on management substantially.
Acknowledgements
This manuscript was submitted on behalf of the OCCAMS Consortium.
Oesophageal Cancer Clinical and Molecular Stratification (OCCAMS) Consortium:
Rebecca C. Fitzgerald1, Paul A.W. Edwards1,2, Nicola Grehan1,5, Barbara Nutzinger1, Aisling M Redmond1, Sujath Abbas1, Adam Freeman1Elizabeth C. Smyth5, Maria O’Donovan1,3, Ahmad Miremadi1,3, Shalini Malhotra1,3, Monika Tripathi1,3, Calvin Cheah1, Hannah Coles1, Matthew Eldridge2, Maria Secrier2, Ginny Devonshire2, Sriganesh Jammula2, Jim Davies4, Charles Crichton4, Nick Carroll5, Richard H.Hardwick5, Peter Safranek5, Andrew Hindmarsh5, Vijayendran Sujendran5, Stephen J. Hayes6,13, Yeng Ang6,7,26, Andrew Sharrocks26, Shaun R. Preston8, Izhar Bagwan8, Vicki Save9, J. Robert O’Neill5,9,20, Olga Tucker10,29, Andrew Beggs10,25, Philippe Taniere10, Sonia Puig10, Gianmarco Contino10, Timothy J. Underwood11,12, Ben L. Grace11, Jesper Lagergren14,22, Andrew Davies14,21, Fuju Chang14,21, Ula Mahadeva14, Francesca D. Ciccarelli21, Grant Sanders15, David Chan15, Ed Cheong16, Bhaskar Kumar16, Loveena Sreedharan16, Irshad Soomro17, Philip Kaye17, John Saunders6,17, Laurence Lovat18, Rehan Haidry18, Michael Scott19, Sharmila Sothi23, George B. Hanna27, Christopher J. Peters27, Krishna Moorthy27, Anna Grabowska28, Richard Turkington30, Damian McManus30, Helen Coleman30, Russell D Petty31, Freddie Bartlett32, Tom D.L. Crosby33
1Early Cancer Institute, Department of Oncology, Hutchison Research Centre, University of Cambridge, Cambridge, CB2 0XZ, UK
2Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge, CB2 0RE, UK
3Department of Histopathology, Cambridge University Hospitals NHS Foundation Trust, Cambridge, CB2 0QQ, UK
4Department of Computer Science, University of Oxford, Oxford, OX1 3QD, UK
5Cambridge University Hospitals NHS Foundation Trust, Cambridge, CB2 0QQ, UK
6Salford Royal NHS Foundation Trust, Salford, M6 8HD, UK
7Wigan and Leigh NHS Foundation Trust, Wigan, Manchester, WN1 2NN, UK
8Royal Surrey County Hospital NHS Foundation Trust, Guildford, GU2 7XX, UK
9Edinburgh Royal Infirmary, Edinburgh, EH16 4SA, UK
10University Hospitals Birmingham NHS Foundation Trust, Birmingham, B15 2GW, UK
11University Hospital Southampton NHS Foundation Trust, Southampton, SO16 6YD, UK
12Cancer Sciences Division, University of Southampton, Southampton, SO17 1BJ, UK
13Faculty of Medical and Human Sciences, University of Manchester, Manchester, M13 9PL, UK
14Guy’s and St Thomas’s NHS Foundation Trust, London, SE1 7EH, UK
15Plymouth Hospitals NHS Trust, Plymouth, PL6 8DH, UK
16Norfolk and Norwich University Hospital NHS Foundation Trust, Norwich, NR4 7UY, UK
17Nottingham University Hospitals NHS Trust, Nottingham, NG7 2UH, UK
18University College London, London, WC1E 6BT, UK
19Wythenshawe Hospital, Manchester, M23 9LT, UK
20Edinburgh University, Edinburgh, EH8 9YL, UK
21King’s College London, London, WC2R 2LS, UK
22Karolinska Institute, Stockholm, SE-171 77, Sweden
23University Hospitals Coventry and Warwickshire NHS, Trust, Coventry, CV2 2DX, UK
24Peterborough Hospitals NHS Trust, Peterborough City Hospital, Peterborough, PE3 9GZ, UK
25Institute of Cancer and Genomic Sciences, University of Birmingham, Birmingham, B15 2TT, UK
26Gastrointestinal Science Centre, University of Manchester, M13 9PL, UK
27Department of Surgery and Cancer, Imperial College, London, W2 1NY, UK
28Queen’s Medical Centre, University of Nottingham, Nottingham, NG7 2UH, UK
29Heart of England NHS Foundation Trust, Birmingham, B9 5SS, UK
30Centre for Cancer Research and Cell Biology, Queen’s University Belfast, Belfast, BT7 1NN, Northern Ireland
31Tayside Cancer Centre, Ninewells Hospital and Medical School, Dundee, DD1 9SY, Scotland, UK
32Portsmouth Hospitals NHS Trust, Portsmouth, PO6 3LY, UK
33Velindre University NHS Trust, Cardiff, Wales, CF15 7QZ, UK