Colorectal Cancer Screening: Landmark Study Shows Early Detection Benefits

A large-scale Swedish study, published in Nature Medicine, confirms the effectiveness of both colonoscopy and fecal immunochemical testing (FIT) in detecting colorectal cancer at earlier, more treatable stages. The findings, from the SCREESCO trial, represent the largest randomized controlled study to date examining colorectal cancer screening methods.

The SCREESCO Trial: A Comprehensive Approach

Colorectal cancer is a significant global health concern, ranking as the third most common cancer worldwide and the second leading cause of cancer-related deaths, according to the World Health Organization (WHO). The SCREESCO (Screening of Swedish Colons) trial, initiated in 2014 and registered with ClinicalTrials.gov, aimed to compare the effectiveness of primary colonoscopy and FIT against usual care – no organized screening.

The study involved 278,280 individuals aged 60 in 18 regions of Sweden. Participants were randomly assigned to undergo either a one-time colonoscopy, two rounds of FIT testing two years apart, or continue with their usual care. The median follow-up period was 4.8 years.

Key Findings: Earlier Detection and Reduced Advanced Cancers

The research revealed that both screening methods led to a higher detection rate of early-stage colorectal cancer compared to the control group. Specifically:

• Colonoscopy: Detected cancer in initial stages in 58.7 cases per 100,000 people per year, compared to 42.5 cases in the control group – a 38% increase.
• FIT Testing: Detected early-stage cancer in 52.7 cases per 100,000 people per year, compared to 44.4 cases in the control group – a 19% increase.

the study showed a decrease in the number of advanced cancer cases (stage III-IV) in both the FIT and colonoscopy groups after four years, compared to those who did not participate in screening.

Preventive Potential of FIT Testing

Researchers observed a trend towards decreasing advanced cancer cases towards the end of the study period in the FIT group. Anna Forsberg, a lead author of the study from Uppsala University, suggested this could indicate a preventive effect of FIT screening through the removal of cancer precursors, such as adenomas. Karolinska Institutet reported on this finding.

Safety Considerations

The study also noted a slight increase in digestive and cardiovascular events in the intervention groups, particularly during the first year after screening. But, the overall number of deaths from any cause was similar across all groups, at approximately 550 deaths per 100,000 people per year.

Participation Trends

Participation rates varied by gender, with higher participation among women for FIT testing and among men for colonoscopy. Most participants had no major pre-existing health conditions.

Understanding Colorectal Cancer

Colorectal cancer typically develops from adenomatous polyps over a period of more than ten years, according to the American College of Gastroenterology. Key risk factors include age, family history, diet, sedentary lifestyle, obesity, and tobacco and alcohol consumption.

Common symptoms can include changes in bowel habits, digestive bleeding, abdominal pain, unexplained weight loss, and iron deficiency anemia. However, the cancer is often asymptomatic in its early stages, highlighting the importance of screening.

Screening Options and Recommendations

The study reinforces the value of organized screening programs in reducing colorectal cancer mortality. Screening options include:

• Colonoscopy: Allows for a complete examination of the large intestine and removal of polyps during the procedure.
• FIT Test: Detects hidden blood in stool and can be performed at home. A positive FIT result requires a follow-up diagnostic colonoscopy.

Dr. Luis Caro, director of the gastroenterology institute Let’s Go in Buenos Aires, emphasized that early detection of colorectal cancer can lead to a cure rate approaching 90%.

Future Research

Follow-up of the SCREESCO trial participants will continue until 2030, with the goal of providing definitive data on the impact of screening on overall colorectal cancer mortality. The study authors express optimism that these findings will demonstrate a reduction in mortality in both intervention groups.