Using risk models based on information about lifestyle and genetics to decide at what age individuals should be invited to screening for bowel cancer could improve both the overall effectiveness and cost effectiveness of the screening programme
Most recently, we explored whether risk stratification using risk models including lifestyle and genetic risk factors could improve the clinical outcomes and cost-effectiveness of bowel cancer screening, without using significant additional screening resources (6). Using MiMiC-Bowel again, we tested the risk models that best predicted bowel cancer in our study in the UK Biobank cohort and compared scenarios that used similar health resources to reflect a resource-constrained system such as the NHS.
- Using an accurate risk model (area under the receiver operating characteristic curve of 0.72) to determine the starting age for screening with two-yearly stool test (faecal immunochemical test, FIT), prevents 218 more bowel cancers and 156 more bowel cancer deaths per 100,000 people compared to a policy of sending the same number of invitations to everyone from age 60.
- It is highly likely (96% probability) that risk-stratification in this comparison is more cost-effective than inviting all individuals at age 60.
- We estimated that the maximum that could be spent on risk stratification and it still be cost-effective is £114 per person.
- The benefits of risk stratification are reduced if the risk model is less accurate, the starting age for screening is lower and the threshold for further testing after the FIT test is higher.. The benefits of risk stratification with currently available models are therefore smaller and will decrease as the starting age of screening is lowered across England.
Using risk models to decide when to invite people for screening could improve the clinical outcomes and cost-effectiveness of bowel cancer screening programmes without using significant additional screening resources. The magnitude of those benefits will depend on the accuracy of the risk models.
Together, this body of work has shown that several models exist that are better than age alone at identifying those at risk of bowel cancer. Before risk stratification can be implemented within the screening programme, however, there are some important additional questions. These include:
- Can risk scores with high enough accuracy to see sufficient benefit from risk stratification be developed for the English population?
- How well do risk models perform in subgroups of the population, including different ethnic groups?
- How might risk assessment be incorporated into screening programmes and how much would that cost?
- Is risk stratification acceptable to the public?
- Which factors are acceptable to the public to use to estimate risk in this context?
- What effects might introducing risk stratification have on uptake of screening? Are those effects outweighed by any potential benefits?
Using risk to determine age at first invitation to screening could represent a resource-neutral means of improving the efficiency of screening and preventing more cancers and deaths from bowel cancer at a lower cost.
The Cambridge and Sheffield research team is addressing some of these questions in ongoing and future work:
Express: Exploring the social and ethical implications of risk stratified screening for society as a whole
A multidisciplinary project with two linked studies using a community jury and a discrete choice experiment to explore views and choices on potential stratified screening programmes. Funded by Cancer Research UK's Early Detection Programme. Read more
STRAT-BCS – Developing a strategy for implementation of risk stratification into bowel cancer screening programmes
This project will explore social and ethical considerations, the views of individuals and the potential impact of a risk stratified approach, and will establish the state-of-the-science and future research and policy requirements for incorporating risk stratification into CRC screening programmes. Funded by National Institute for Health Research Advanced Fellowship. Read more
- Risk Prediction Models for Colorectal Cancer: A Systematic Review. Juliet A Usher-Smith, Fiona M Walter, Jon D Emery, Aung K Win, Simon J Griffin. Jan 2016. Cancer Prev Research.
- External validation of risk prediction models for incident colorectal cancer using UK Biobank. J A Usher-Smith, A Harshfield, C L Saunders, S J Sharp, J Emery, F M Walter, K Muir, S J Griffin. Jan 2018. British Journal of Cancer.
- Risk Prediction Models for Colorectal Cancer Incorporating Common Genetic Variants: A Systematic Review. Luke McGeoch, Catherine L. Saunders, Simon J. Griffin, Jon D. Emery, Fiona M. Walter, Deborah J. Thompson, Antonis C. Antoniou, and Juliet A. Usher-Smith. July 2019. Cancer Epidemiology, Biomarkers and Prevention.
- External Validation of Risk Prediction Models Incorporating Common Genetic Variants for Incident Colorectal Cancer Using UK Biobank. Catherine L. Saunders, Britt Kilian, Deborah J. Thompson, Luke J. McGeoch, Simon J. Griffin, Antonis C. Antoniou, Jon D. Emery, Fiona M. Walter, Joe Dennis, Xin Yang, and Juliet A. Usher-Smith. Feb 18 2020 Cancer Prev Research.
- Should colorectal cancer screening start at different ages for men and women? Cost-effectiveness analysis for a resource-constrained service. Chloe Thomas, Olena Mandrik, Sophie Whyte, Catherine L. Saunders, Simon J. Griffin, Juliet A. Usher-Smith. Feb 02 2021. Cancer Reports.
- The costs and benefits of risk-stratification for colorectal cancer screening based on phenotypic and genetic risk: a health economic analysis. Chloe Thomas, Olena Mandrik, Catherine L. Saunders, Deborah Thompson, Sophie Whyte, Simon Griffin, Juliet A. Usher-Smith. May 26 2021. Cancer Prev Research.
Primary Care Unit, Department of Public Health and Primary Care, University of Cambridge
School of Health and Related Research, University of Sheffield
UK National Screening Committee - GOV.UK
This briefing was written by Lucy Lloyd, Dr Juliet Usher-Smith, Dr Chloe Thomas and Professor Simon Griffin. Published May 27 2021 by the Primary Care Unit, University of Cambridge