Screening linked to 43% lower colorectal cancer mortality

A stool-test kit arrives at the homes of people aged 60–74 in Sweden, asking for a sample that can reveal blood too small to see. In the Stockholm–Gotland screening program, people who took part had a 43% lower risk of dying from colorectal cancer, according to a study tracking participants for up to 14 years.

The researchers at Karolinska Institutet and Umeå University studied 376,511 people invited to screening between 2008 and 2012. The program, introduced in Stockholm and Gotland as early as 2008, sends a kit every two years. A positive result typically leads to further investigation, usually a colonoscopy, where doctors can examine the bowel more closely.

The result is stronger than an earlier assessment of the same program. That analysis found a 14% lower risk of dying from colorectal cancer among people who received an invitation. The new study estimated a 26% lower risk for invitation alone, and a 43% lower risk among those who actually participated.

That distinction matters because screening only works when the sample is returned. Around one-third of people do not submit one, even though the test is free and offered at home. During the study’s follow-up, 1,668 deaths from colorectal cancer were recorded.

So, concretely, the study highlights the importance of completing the test: participation was linked to a markedly lower risk of death in this large, long-running study. The result does not prove that screening alone caused every difference. The researchers used statistical adjustments to address factors such as later access to screening and nonadherence, and they say some uncertainty remains. The estimates were published in JAMA Network Open.