New research is bolstering the evidence for the benefits of colorectal cancer screening, demonstrating that both colonoscopy and fecal immunochemical testing (FIT) lead to earlier detection of the disease. A large clinical trial conducted in Sweden, published in in Nature Medicine, found that both screening methods resulted in a higher proportion of cancers diagnosed at an early stage, compared to those without organized screening programs.
The study, known as SCREESCO (Screening of Swedish Colons), is one of the few worldwide to directly compare colonoscopy and FIT in a real-world setting. Researchers followed over 278,000 individuals aged 60, none of whom had a prior diagnosis of colorectal cancer, across 18 regions of Sweden. This robust design, with its comprehensive data collection and minimal loss to follow-up, provides a strong foundation for the findings.
Three Groups, a Common Goal
Participants were randomly assigned to one of three groups: those invited to undergo a one-time colonoscopy; those invited to two rounds of FIT, analyzing stool samples for traces of blood with a low positivity threshold (10 micrograms of hemoglobin per gram of feces); and a control group receiving usual care – meaning no organized screening invitation.
Over a median follow-up period of 4.8 years, researchers tracked cancer diagnoses, stage at detection, and adverse events, including gastrointestinal and cardiovascular issues. The key finding was a “stage shift” – a trend towards diagnosing more cancers at earlier stages (I and II) in the screening groups.
Specifically, the colonoscopy group showed a 38% increase in early-stage colorectal cancer diagnoses compared to the control group. The FIT group experienced a 19% increase in early detection compared to those not invited to screening. Conversely, the proportion of more advanced cancers (stages III and IV) was lower in the screened groups.
The reduction in advanced cancers was particularly notable in the FIT group, a clinically significant finding as these later stages are associated with higher mortality rates and more aggressive treatment regimens. This pattern aligns with the expected outcome of early detection programs: identifying previously undetected cancers, ultimately leading to a decrease in the number of advanced cases.
Weighing the Risks and Benefits
The study also addressed potential adverse effects of screening, a critical consideration for population-level programs. During the first year following the screening invitation, a slight increase in gastrointestinal and cardiovascular events was observed in both the colonoscopy and FIT groups compared to the control group. However, this difference diminished over time.
By the end of the follow-up period, overall rates of cardiovascular events were similar across all groups, and there was no significant difference in all-cause mortality. The FIT group experienced a slight increase in gastrointestinal bleeding, primarily linked to therapeutic procedures following the detection of precancerous lesions. Researchers noted that serious adverse events directly attributable to colonoscopy were rare, occurring in only 0.2% of cases – including intestinal perforations and major bleeding.
Implications for Public Health Policy
The SCREESCO trial was conducted in a unique context: a population largely unscreened, a country with robust health records, and nearly complete participant tracking. This allowed researchers to assess not only cancers detected through the program but all diagnoses within the healthcare system during the study period.
While the follow-up period is currently insufficient to determine whether screening ultimately reduces colorectal cancer mortality – the primary endpoint of the trial, which will be evaluated until – the current results reinforce the idea that both colonoscopy and FIT are effective tools for detecting the disease at more treatable stages.
According to Marcus Westerberg, docent at Uppsala University and the study’s corresponding author, the initial increase in diagnoses is a potentially positive sign. He explained that the findings suggest that screening programs can shift the balance towards earlier detection and improved treatment outcomes.
The study’s findings are particularly relevant as screening recommendations have evolved in recent years. In the United States, the American Cancer Society lowered the recommended age to begin colorectal cancer screening from 50 to 45 in , and the United States Preventive Services Task Force followed suit in . A separate study, published in August , showed a surge in colorectal cancer screening among adults aged 45-49, with colonoscopy screening increasing by 43% and stool-based testing increasing more than fivefold from to .
The researchers emphasize that the balance between the benefits of early detection and the potential harms of screening will be crucial for informing public health decisions, especially in countries aiming to expand or implement organized screening programs. The study suggests that actively inviting the population to undergo FIT or colonoscopy not only changes *when* colorectal cancer is diagnosed but may also improve long-term treatment prospects.
