More cases of colorectal cancer are detected at an early stage with screening. This is according to new research based on data from over 278,000 60-year-olds, who were randomly selected to undergo one of two interventions or no screening at all (usual care). The study, which is a collaboration between Uppsala University and Karolinska Institutet, has been published in Nature Medicine.
Cancer of the colon and rectum, known as colorectal cancer, is one of the most common cancers. Prevention and early detection are crucial to reducing the risk that the patient will die from the disease. In a new study, researchers at Karolinska Institutet and Uppsala University investigated whether screening is a beneficial method for detecting cases of colorectal cancer at an early stage.
The study involved over 278,000 people who were randomly offered either a primary colonoscopy; two faecal immunochemical tests (FIT), where the patients provided a stool sample, which was followed by a colonoscopy if one of the samples was positive; or no intervention at all, termed usual care.
"The results show that both types of screening lead to more cases of early-stage cancer being detected, especially in the first two years when most of the interventions were carried out. This is good news because, more often than not, cancer that is diagnosed early can be successfully treated. For many types of cancers, there is no preventive treatment option, but in this case, it is also possible to detect and remove adenoma – precursors that might otherwise have developed into cancer," says Marcus Westerberg, docent at Uppsala University and the study's author for correspondence.
Based on a study that started in 2014
The research is part of the Swedish study SCREESCO, which started in 2014 to investigate how effective two different screening methods are in reducing long-term mortality from colorectal cancer. The participants were 60 years old, identified via the population register, and then randomised into three different groups:
- Primary colonoscopy – these participants were called to undergo a colonoscopy.
- Faecal immunochemical test (FIT) – these participants did two faecal tests in their own homes. If at least one of the samples showed a positive result, which was measured by the amount of blood they had in their stool (10 μg Hb/gr), they underwent a colonoscopy. The participants in this group were offered this test twice: in year one and year three.
- Usual care – participants did not undergo either intervention but were used as a control group.
In patients where the precursors to cancer were found in a colonoscopy, they received treatment according to the current guidelines. The participants were then followed via the register until 2020.
Removes the precursors to cancer
At the end of the follow-up period, the researchers found that the number of cases of more advanced colorectal cancer had decreased in both of the intervention groups. The clearest results were seen in the group where the participants had done FITs. There, 0.61 per cent developed colorectal cancer, compared to 0.73 per cent in the control group.
"We can show that cases of advanced cancer tend to decrease towards the end of the period in the group that was randomised to provide stool samples for FIT. This could be evidence of a preventive effect of the screening, through the removal of the precursors to cancer," says Anna Forsberg, docent at Karolinska Institutet, who is the last author and responsible for SCREESCO.
The three groups to be followed until 2030
The study also investigated whether there were any negative effects associated with an increased number of colonoscopies. The researchers were able to see a slight increase in stomach and intestinal bleeding as well as blood clots in these patient groups, especially in the first year when most of the colonoscopies were performed. However, these events were unusual, and the all-cause mortality rate was the same in all groups.
The researchers now plan to follow the participants in the study until 2030 to see how effective the different screening methods are in reducing long-term mortality from colorectal cancer.
"This study gives us great hope that screening will also be shown to reduce mortality from colorectal cancer in both groups when the study is finally evaluated in about five years," says Anna Forsberg.
Facts in brief
The Swedish study SCREESCO started in 2014 to investigate how effective two different screening methods are in reducing long-term mortality from colorectal cancer. The study compares screening with once-only colonoscopy and screening with two rounds of two-stool FIT with a low cutoff for a positive FIT of 10 μg Hb/gr for both men and women.
In Sweden, screening with a faecal immunochemical test (FIT) has been offered every two years in Region Stockholm and Region Gotland since 2015 to individuals aged 60–69 years, and since 2020 to individuals aged 60–74 years. The cutoff values for a positive FIT were then 40 μg Hb per gram of stool for women and 80 μg Hb/gr for men. Individuals with a positive FIT are offered colonoscopy. A national, FIT-based screening programme with the same cutoff values, testing frequency, and age range started being rolled out in 2021 with full implementation planned for 2026.
