Bold truth: screening saves lives by catching colorectal cancer early. But here’s where it gets controversial: the best approach isn’t a one-size-fits-all answer, and different screening methods may work better for different people. Here’s a fully rewritten, expanded take on the study, keeping all key information intact while making it clearer for beginners.
Screening Boosts Early Detection of Colorectal Cancer
Researchers from Uppsala University and Karolinska Institutet conducted a large, randomized clinical trial to compare how well two screening methods detect colorectal cancer at an early stage. The findings, published in Nature Medicine, come from the Swedish SCREESCO study, which began in 2014. Colorectal cancer, involving the colon or rectum, is among the most common cancers worldwide. The study focused on whether early detection through screening translates into more cancers found at an early, more treatable stage.
Why early detection matters
Early detection matters because cancers found at an early stage are generally easier to treat successfully. The study looked at two screening strategies and compared them to a control group with no screening intervention. All participants were 60 years old at enrollment. The large sample included more than 278,000 individuals randomly assigned to one of three groups:
- Primary colonoscopy: all participants in this group underwent a single colonoscopy.
- Two rounds of fecal immunochemical testing (FIT): participants provided stool samples, and if at least one sample tested positive, they received a colonoscopy.
- Control: no screening intervention.
Key findings
- Both screening methods increased the number of cancers detected at an early stage, particularly within the first two years when most screening activities occurred. Early detection is especially valuable because it often allows cancer to be treated more successfully.
- The study notes the additional benefit of identifying and removing adenomas (precursors to cancer) during screening, which can prevent cancer from developing in the first place.
- Among those who received FIT screening, a smaller percentage developed colorectal cancer by the end of the study period (0.61%) compared with the control group (0.73%), suggesting a preventive effect beyond early detection.
- The researchers followed participants through 2020 and observed that the rate of advanced colorectal cancer tended to decline over time in the FIT group, supporting the idea that removing precursors may reduce later cancer progression.
Author insights
Anna Forsberg, a senior author from Karolinska Institutet, emphasizes that the reduction in advanced cancers toward the end of the follow-up period in the FIT group may reflect a preventive impact from removing cancer precursors during screening. Marcus Westerberg, a corresponding author from Uppsala University, notes that detecting and treating precursors during colonoscopy is aligned with current guidelines and contributes to better outcomes.
Safety and long-term follow-up
The trial also monitored for potential harms associated with more colonoscopies. There were rare increases in stomach and intestinal bleeding and blood clots, particularly in the first year when most procedures occurred. Importantly, the overall mortality rate did not differ among the groups, indicating that the screening approaches did not raise the risk of death from any cause during the study period.
Next steps
Participants will continue to be followed through 2030 to assess long-term effects on mortality from colorectal cancer. Researchers hope to determine whether both screening strategies continue to reduce cancer deaths over time, beyond the early gains in detection.
Implications for screening programs
- Nationwide programs: Sweden began rolling out a national screening program in 2021, with full implementation planned for 2026. It offers FIT every two years to individuals aged 60–74, with follow-up colonoscopy if the FIT result is positive.
- Positive thresholds vary by sex: thresholds cited include 40 μg Hb per gram of stool for women and 80 μg Hb per gram for men. A separate SCREESCO comparison examined one-time colonoscopy and two rounds of FIT with a lower 10 μg Hb per gram cutoff for both sexes.
Bottom line
This large, well-conducted trial demonstrates that screening—whether via colonoscopy or FIT—improves early detection of colorectal cancer and reduces progression to advanced disease for some groups. While FIT screening showed the clearest signals of benefit in this study, the choice of screening method may depend on individual risk factors, access to testing, and personal preferences. Do you think FIT or colonoscopy should be the default screening method in public programs, or should a personalized approach be emphasized? Share your thoughts in the comments.
