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WHO Classification of Tumours: a Living Evidence Gap Map by Tumour Type 





Visit the main WCT EVI MAP website



The WHO Classification of Tumours (WCT) is a global reference for pathologists, oncologists, surgeons, and researchers, and forms the histopathological basis of cancer diagnosis around the world. It is vital that the WCT is informed by the best available evidence, but the risk of incorporating misinformation into the clinical decisions pathway exist.


We aim to map the evidence cited in the WCT with the aim of improving future editions and guiding cancer researchers in where to direct efforts in generating new data. This project will actively involve members of the WCT editorial and authorship team. 


We will be using a novel method known as an Evidence Gap Map (EGM) and this will help identify gaps and pockets of low‐level evidence in current the WCT volumes. We will map and rank the evidence in the WCT using a new hierarchy of evidence for tumour pathology, which will be developed bespoke for this project using a Delphi study. 


The resulting EGMs will increase the discoverability and use of studies by the WCT decision‐makers, research commissioners and researchers, and will represent a ground‐breaking advance for the research in the field, impacting over time positively in cancer diagnosis and management.


IARC has received a €3.5 million Horizon grant from the European Commission, which in the UK is delivered by Innovate UK (UKRI).


This project is being developed under IARC’s leadership, led by Dr Ian Cree, along with researchers at the Oxford University (NDS), the DHM German Heart Centre (Munich), ISCIII Páginas - Instituto de Salud Carlos III,  ScHARR School of Health and Related Research, University of Sheffield, Institute Curie (Maria Sklodowska-Curie National Research Institute of Oncology), and Singapore General Hospital.

WCT EVI MAP website launched

Press release

NDS news


WCT EVI MAP Delphi Study: Evidence Levels in Pathology

go to the new levels of evidence here

Participant Information Sheet

If you have been invited to take part in the Delphi study, a copy of the participant information sheet is below.


Thank you for taking the time to respond to the invitation you have received. IARC is inviting you to take part in a survey study using a methodology called Delphi. This study design is used as an attempt to reach a consensus on complex issues, amongst a group of expert peers. This is the first of several short surveys that we will send you for this study over the next few months. This survey should take no more than 10-15 minutes to complete.

Before you decide whether to take part it is important for you to understand why the research is being done and what it will involve. Please take time to read the following information carefully, as this will be important for you to understand the survey questions. Please contact us if there is anything that is not clear or if you would like more information.

Why is this research being conducted? 

The aim of this study is to develop and reach a consensus on how to rank various study types used as a basis for pathology tumour classification – a new hierarchy of evidence for pathology. This new hierarchy will be used to evaluate the evidence-base currently supporting the WHO Classification of Tumours (often referred to as the WHO ‘blue books’). This study forms just one part of a wider project known as ‘Mapping the Evidence for the WHO Classification of Tumours: a Living Evidence Gap Map by Tumour Type’ (WCT EVI MAP). WCT EVI MAP aims to map, rank, and evaluate the evidence cited in the blue books in order to establish the quality of the current literature base, identify gaps or pockets of low-value evidence, and direct future research to improve the literature-base where lacking. This is part of a concept being advocated by IARC known as Evidence-Based Pathology. We will also publish our hierarchy and envisage that it will be more widely adopted in the pathology community.

What is the background to this?

The concept of ‘levels’ or a ‘hierarchy’ of evidence is well established in the evidence-based medicine movement. The basic premise of these levels of evidence is that some types of study design are inherently biased and others are less so. It is often said that randomised controlled trials (RCTs) are of the highest ‘quality’ because they have the lowest risk of bias, whereas studies such as case reports are of much lower quality because they have significant risk of bias. Over the years, there have been various models suggested to reflect this hierarchy, one example is outlined below.


Level 1  Systematic reviews of randomised trials

Level 2  Randomised trials

Level 3  Non-randomised cohort trials or follow-up studies

Level 4  Case-series or case-control studies

Level 5  Mechanism-based studies, basic science, expert opinions

OCEBM Levels of Evidence Working Group. The Oxford Levels of Evidence 2. Available from:

What is the problem we are trying to solve? 

Most pathologists or pathology focused cancer researchers recognise that existing hierarchies of evidence, like the one above, are heavily focused on interventions such as drug treatments, and are not always easy to apply to diagnostics, prognostics, or tumour classification. We want to address this issue by developing a novel and bespoke hierarchy for tumour pathology research. We do not aim to replace existing hierarchies, but to add a new and complementary system.

Why have I been invited to take part? 

You have been identified to take part because you are a member of IARC or the blue book editor/authorship team and we believe you have expert knowledge specific to this problem. We very much appreciate your interest in participating and hope you agree to proceed.

General Information 

You may ask any questions before deciding to take part by contacting one of the team (see later). A copy of this participant information sheet and the following consent form can be provided on request. The participation sheet, consent form, and survey are only available in English.

What will happen to me if I take part in the research? 

You will first be asked to complete an online consent form. Then you will be asked to complete a short online survey about your views on how the new hierarchy of evidence should be constructed. No personal details or identifiable data will be collected.

The majority of questions will ask you to select from a list of options, although some anonymous free text boxes will be included.

The Delphi method that this study uses requires more than one standalone survey, you will be contacted again in the future to follow-up with additional rounds of surveys, which will have a very similar structure. This is because not all the questions can be asked until a consensus is reached (i.e. decisions are made) on the more basic aspects of the hierarchy. It may be necessary to ask the same questions again, in order to attempt to refine or reach consensus. We define consensus as a threshold of 75% of participants agreeing with each other in the survey answers. Your participation in future rounds is not compulsory if you complete this survey, and we will not be able to identify if you have taken part or not, in this or future rounds.

Future surveys will present some of the results from the earlier surveys, to help you make a decision on how to proceed. You will be guided through the practicalities of the process at every step, but you will be able to freely give the answers and views that you have. All of the surveys will be short and anticipated to take around 10-15 minutes of your time at the most.

Do I have to take part?

No, participation is voluntary. Please read this information before agreeing to participate. The consent to proceed (if you wish to) will follow shortly. If you do decide to take part, you may withdraw at any point before finishing the survey by closing the browser/window, and data will not be recorded. You can withdraw for any reason, without needing to give that reason. All answers are collected anonymously, therefore if you have finished the survey and your answers are submitted, it is not possible to delete the responses you have given unfortunately. You do however have the ability to decline taking part in future rounds/surveys.

What are the possible disadvantages and risks in taking part?

No disadvantages or significant risks are expected from your participation.  

Are there any benefits in taking part?

There is no direct or personal benefit to you by participating in the project although it is anticipated that this study will be extremely impactful and will influence not only the direction and quality of evidence in the future WCT blue book series but will influence many areas of pathology.

What information will be collected and why is the collection of this information relevant for achieving the research objectives?

We will not ask you to provide any information that would directly identify you. Some brief questions about your specialty / areas of work will be asked to establish your basic background at each survey. The questions will then focus on your opinions about evidence used in pathology.

Your IP address will not be stored.

Will the research be published? Could I be identified from any publications or other research outputs?

The findings from the research will be published, and conference posters/presentations are likely. The new hierarchy will be used in the WCT EVI MAP project. Any comments you provide may be publicised/published, but these will remain anonymised.

Who will have access to the data?

The Online Survey Provider JISC is collecting data ( JISC will share data with the University of Oxford for the purposes of this research.  This will not contain any information that could directly identify you.

The University of Oxford and JISC are the data controllers with respect to your data and, as such, will determine how your data is used in the research. The University will process your data for the purpose of the research outlined above. Research is a task that we perform in the public interest. Further information about your rights with respect to your data is available from

JISC’s privacy notice can be viewed at

Analysed and summarised results will be presented to participants at each subsequent round/survey and will be published in due course.

Who has reviewed this study?

This project has been reviewed by, and received ethics clearance through, a subcommittee of the University of Oxford Central University Research Ethics Committee [application approval number R83130/RE001].

Who do I contact if I have a concern, or I wish to complain?

If you have a concern about any aspect of this study, please speak to Richard Colling ( and I will do my best to address your concerns. I will acknowledge your concern within 10 working days and give you an indication of how it will be dealt with. If you remain unhappy or wish to make a formal complaint, please contact the Chair of the Medical Sciences Interdivisional Research Ethics Committee at the University of Oxford who will seek to resolve the matter as soon as possible:

Email:; Address: Research Services, University of Oxford, Boundary Brook House, Churchill Drive, Headington, Oxford OX3 7GB

Who is funding the research?

This study is funded by the European Commission Horizon scheme and Innovate UK (UK Research and Innovation).

Further Information and Contact Details

If you would like to discuss the research with someone beforehand (or if you have questions afterwards), please contact:

The study lead Dr Richard Colling (, the WCT EVI MAP principal investigator Dr Ian Cree, IARC (, or the project assistant Laura Brispot (

Consent Form (copy)

Please note that you may only participate in this survey if you are 18 years of age or over. If you have read the information above and agree to participate with the understanding that the data you submit will be processed accordingly, please tick the box below to start.

I certify that I am 18 years of age or over: YES/NO

Yes, I agree to take part: YES/NO