The impact of COVID-19 on colorectal cancer screening and outcomes

By Dr. Liji Thomas, MDJul 24 2023Reviewed by Lily Ramsey, LLM

Colorectal cancer (CRC) accounts for many deaths due to malignancy. Screening is known to enable early detection and the removal of precancerous lesions, reducing the cancer burden.

The effect of the coronavirus disease 2019 (COVID-19) pandemic on such programs is explored in a recent paper published in eClinical Medicine as part of The Lancets Discovery Series.

Study: Potential global loss of life expected due to COVID-19 disruptions to organised colorectal cancer screening. Image Credit: mi_viri/Shutterstock.com

Introduction

CRC screening is carried out for asymptomatic individuals with no risk factors for this cancer. Primary screening depends on a fecal test, with a subsequent diagnostic colonoscopy if indicated by a positive test, or primary screening by colonoscopy.

Most organized programs for CRC screening are in wealthy countries, while pilot programs have been set up in Asia and South America. Organized screening is supplemented by opportunistic screening, done on an individual or sometimes through an insurer.

COVID-19 interrupted the smooth running of these programs to varying extents. Studies such as the present one are important in planning for future disruptions due to an overwhelming public health emergency when cancer screening and such non-emergency medical programs tend to be put on the back burner at individual and policy levels.

In Australia, where the program was not officially stopped, even temporarily, the number of participants in organized screening dropped by over half. CRC being a slow-growing lesion, the full impact of paused screening or of individual unwillingness to take advantage of such programs may take time to manifest.

Computational modeling may be very useful in shaping policies during such periods when decisions must be taken despite the lack of objective data.

The current study is one such attempt, where the scientists looked at screening programs for CRC from 29 countries worldwide. They examined participation rates and changes in screening practices in 2020 because of the pandemic.

They used four different models to assess the long-term impact of COVID-19 on the number of cases and deaths from CRC. This compensated for the inability to develop customized models for each country.

“This approach to global modeling by simulating a core set of imputed screening programs and extrapolating may be useful in future global epidemiological modeling.”

Excess mortality rates were used in lieu of participation data to arrive at such data in those countries where such information was not available for that year.

The researchers also simulated catch-up programs requiring additional screening in 2021 to mitigate the adverse impact of COVID-19-related measures and adaptations.

What did the study show?

In countries with participation data for 2020, the model results showed reduced CRC screening. The reduction ranged from just above 1% to 40%.

There were over seven million fewer fecal screening tests for CRC globally in 2020 globally. About 40% of the deficit occurred in countries with organized screening vs. the rest in countries where screening data was unavailable.

The decreased participation in screening would result in over 10,500 CRC diagnoses in 2020. These would be caught possibly in more advanced stages of the disease or during later screening rounds.

If catch-up screening were not carried out in 2021, this would mean 13,000 more cases of CRC and almost 8,000 more deaths than expected between 2020 and 2050. On the other hand, these figures would be lowered by nearly 80% and 85%, respectively, by such compensatory screening programs.

Any decrease in CRC screening would cause a higher cancer burden over 2020-2050. For instance, opportunistic screening was missed in almost four million individuals in the USA from March to May 2020. This could result in nearly 41,000 cases of CRC, with 17,000 deaths, by 2050.

Conversely, the scientists found that catch-up screening would reduce cases and mortality by 73–88% and 81–94%, respectively.

What are the implications?

The interruption of routine medical care, such as CRC screening, because of the pandemic is likely to cause an increase in CRC cases and mortality. However, properly conducted catch-up screening could capture most excess cases and prevent most excess deaths.

“Careful management of any disruption is key to improving the resilience of colorectal cancer screening programs.”

The current study modeled various scenarios to cover a range of possibilities, making it likely that the observed disruption and the impact for any given country would lie within this range. Similar is the case for catch-up screening, where the rate will be somewhere between ‘no catch-up’ and ‘full catch-up.’

Despite the administrative difficulties of catch-up screening, it is important to prioritize it in view of the loss of human health and lives.

For instance, the scientists found that mass media campaigns could be expensive and cost-effective in bringing more people into the screening net, thus avoiding unnecessary deaths from CRC.

Other measures include managing the capture rate from catch-up screening. For instance, healthcare systems could consider adjusting screening thresholds or having a longer interval for catch-up screening, thus helping those at higher risk to get the earliest care.

Despite the limitations in data availability, such modeling studies could help improve policies to reduce the impact of large-scale disruptions such as those caused by the COVID-19 pandemic.