by Dr Róisín McCarthy, Research Officer, National Screening Service
We recently contributed to the publication of an international article in The Lancet Journal titled ‘Potential global loss of life expected due to COVID-19 disruptions to organised colorectal cancer screening’. We provided national bowel screening data from the years 2018/2019 to the authors of the publication.
Background to the study
Bowel screening aims to detect abnormalities in the bowel in people who do not have symptoms, so that timely diagnosis and early treatment can be offered. Eligible people who wish to take part in bowel screening are required to collect a faecal (poo) sample using a screening test kit (faecal immunochemical test (FIT) which is sent to an accredited laboratory for analysis. Many organised screening programmes exist worldwide. The COVID-19 pandemic has had a significant impact on healthcare systems since 2020 and has affected cancer screening programmes globally with some programmes completely suspending screening and others experiencing significant decreases in participation and diagnostic follow-up. This study aimed to estimate the global effects of reduced screening activity on bowel screening outcomes, gather real-world country-level screening data to estimate changes to screening numbers in countries where direct data were not available, and estimate the benefits of providing catch-up screening to people whose screening was delayed due to the pandemic.
Methods of the study
Organised screening programmes were reviewed in countries worldwide to identify programme information, pre-2020 screening rates and, where available, screening rates for 2020. For programmes where 2020 screening rates were not available, potential screening uptake rates were calculated based on local excess mortality rates during 2020. Four independent computer programme models were used to estimate the potential impact of changes to screening participation rates in 2020 on long-term bowel cancer burden for each organised screening programme. Estimates at country-level were combined to generate global estimates.
Results of the study
- Review of organised screening programmes worldwide
Thirty-one countries and regions were identified as having organised screening programmes with sufficient data to inform modelling. These countries showed cancer screening participation rates ranging from 13.8% to 74.7% pre-COVID. In 10 countries where screening participation data were available in 2020, organised bowel cancer screening numbers had a decreased range of 1% to 40%.
- Calculated estimates of bowel cancer health outcomes based on computerised modelling programme
Computerised modelling estimated that there would have been over 7 million fewer bowel screening tests globally in 2020 due to the COVID-19 pandemic. In 2020, globally there would be over 10,000 bowel cancer diagnoses, which would be diagnosed either at later screening rounds or potentially at a later disease stage. In the absence of catch-up screening programmes, it was projected that there would be 14,000 additional cases of bowel cancer and almost 8,000 more deaths than expected in the next 30 years. For those screened once every two years and who were not screened due to the pandemic, 79% of additional cases and 85% of additional deaths could have been prevented with catch-up screening in 2021. In Ireland, based on relative 25% screening decreases in 2020, the model predicted that there would be a reduction of 27,704 screening tests in 2020. The model also predicted that if there was a full catch-up screening programme in place in Ireland in 2021, there would be no additional cases or deaths in the next 30 years.
- Ireland’s recovery programme for bowel screening
The focus of the National Screening Service programmes’ restart has been to achieve a maximum screening invitation rate that is compatible with a safe and controlled follow-up assessment and treatment capacity within the health service. All screening services involve population-based screening for people without any symptoms. Due to the COVID-19 pandemic in March 2020, the BowelScreen programme deferred the issuing of screening invitations. The programme resumed issuing new invitations on a phased basis in August 2020. Any outstanding participants who were due to be invited for screening in 2020 were brought forward for invite to 2021 (approx. 120,000 people). The aim of the BowelScreen recovery plan was to maximise available endoscopy capacity. Measures to increase capacity included insourcing at weekends and engagement with new endoscopy units for the provision of colonoscopy services. Targeted communications campaigns were used to encourage those who received invitations to follow them up.
Implications of this study
COVID-19 significantly disrupted organised bowel cancer screening globally. Results of this study show that catch-up screening can ease the long-term adverse effects on bowel cancer burden by reducing excess cases and deaths by up to 80%. This study highlights the importance of catch-up screening programmes and managing the capture rate from catch-up screening. Mass-media campaigns aimed at improving screening participation can be cost-effective to help screening return to pre-COVID levels and to avoid unnecessary deaths from bowel cancer. Modelling studies like this could help inform policies to reduce the impact of large-scale disruptions such as those caused by the COVID-19 pandemic. By carefully planning and designing screening programmes to be resilient to future disruptions, health systems can reduce the impact on population health.