Colorectal cancer is among the most common cancers, but outcomes are generally favorable when the disease is found early. Sweden has introduced universal screening, with people aged 60-74 offered testing every two years.

Participants receive a screening kit at home and are asked to provide a stool sample. The sample is checked for tiny amounts of blood that cannot be seen with the naked eye. If blood is found, additional testing is offered, most often a colonoscopy.

Long-Term Data Show a Larger Benefit

Stockholm and Gotland began routine colorectal cancer screening as early as 2008. Researchers from Karolinska Institutet and Umeå University have now tracked participants for up to 14 years to examine how screening may affect the risk of dying from the disease.

"A previous evaluation of the program showed that those who received an invitation to screening had a 14 percent lower risk of dying from the disease," says Johannes Blom, senior consultant and associate professor at the Department of Clinical Science and Education, Södersjukhuset, Karolinska Institutet, and the study's corresponding author. "We have now been able to show that the mortality is significantly lower than that among those who actually take part in the screening."

Participation Was Linked to a 43 Percent Lower Death Risk

The researchers compared people invited to screening between 2008 and 2012 with a control group whose members were either invited later or were not invited at all. They then used statistical methods to account for factors that could influence the findings, including people in the control group who later became eligible to participate and people who were invited but chose not to take part.

After those factors were considered, receiving an invitation to screening was associated with a 26 percent lower risk of dying from colorectal cancer. Among people who actually participated, the risk was 43 percent lower.

"Although screening is offered free of charge and the test is simple to carry out, around a third of people do not submit a sample," says Johannes Blom. "Our study highlights the importance of taking part in colorectal cancer screening, and shows that it can actually save lives."

More Than 376,000 People Were Followed

The study included 376,511 people. Over the follow-up period, researchers recorded 1,668 deaths from colorectal cancer.

The large number of participants, the lengthy follow-up period, and access to Swedish health registers were among the study's key strengths. However, the researchers note that the estimates depend on statistical adjustments designed to account for different sources of bias, so some uncertainty remains.

The study was funded by the Swedish Cancer Society, the Swedish Research Council and Region Stockholm. The researchers state that they have no conflicts of interest.