SCREESCO Trial Reports Colorectal Cancer Screening Shifts Diagnoses to Earlier Stages; Long-Term Mortality Data Awaited

SCREESCO Study Reveals Early Detection Boost and Reduced Advanced Colorectal Cancer Cases

A large-scale study, known as SCREESCO, has investigated the effectiveness and potential harms of colorectal cancer screening methods in over 278,000 Swedish adults. The research indicates that both primary colonoscopy and Fecal Immunochemical Test (FIT) screening lead to an increased detection of early-stage colorectal cancers and a reduction in advanced cases within a specific timeframe. While short-term adverse events were noted, all-cause mortality rates remained consistent across all groups during the initial follow-up period.

Both primary colonoscopy and Fecal Immunochemical Test (FIT) screening lead to an increased detection of early-stage colorectal cancers and a reduction in advanced cases within a specific timeframe.

Study Overview

The SCREESCO study, a collaboration between Uppsala University and Karolinska Institutet, commenced in 2014. Its primary aim was to evaluate the long-term effects of two distinct colorectal cancer screening methods. The initial findings, tracking participants until 2020, were recently published in Nature Medicine.

Methodology

Participants in the trial, all 60-year-old Swedish adults, were randomly assigned to one of three groups:

• Primary Colonoscopy Screening: Individuals in this group underwent a direct colonoscopy.
• Fecal Immunochemical Test (FIT) Screening: This group received two rounds of two-stool FIT screening, using a 10 μg hemoglobin per gram of feces threshold. A colonoscopy followed if a sample tested positive.
• Usual Care (Control Group): Participants in this group received no invitation to screening.

The study assessed diagnostic yield, total colorectal cancer cases, and adverse events over a median follow-up period of approximately 4.8 years.

Key Findings

Both screening methods demonstrated a significant increase in the detection of early-stage colorectal cancer.

• The colonoscopy group showed a 38% higher rate of early-stage detection compared to the control group.
• The FIT group had a 19% increase in early-stage detection.
• Conversely, late-stage colorectal cancers were less common in individuals who underwent screening.
• Screening also enabled the detection and removal of adenomas, which are precursors to cancer.

By the end of the initial follow-up period in 2020, a reduction in advanced colorectal cancer cases was observed in both intervention groups.

• The FIT group recorded 0.61% of participants developing colorectal cancer, compared to 0.73% in the control group.
• Researchers suggest this indicates a preventive effect of screening through the removal of cancer precursors.
• However, the total number of colorectal cancer cases across all groups remained similar during this diagnostic-phase follow-up.
• This suggests that screening advanced the timing of detection rather than reducing the overall incidence within this initial timeframe.

A temporary increase in stomach and intestinal bleeding, as well as blood clots, or gastrointestinal and cardiovascular events, was noted in the screening groups. These events were particularly evident within the first year, when most colonoscopies were performed. These events were described as infrequent. Serious colonoscopy-related adverse events occurred at a rate of 0.2%.

The all-cause mortality rate remained consistent across all groups during the study period, indicating no short-term impact on overall death rates from screening. The trial was not specifically designed to assess colorectal cancer-specific mortality during this initial phase.

The all-cause mortality rate remained consistent across all groups during the study period, indicating no short-term impact on overall death rates from screening.

Future Outlook

Participants in the SCREESCO study will continue to be followed until 2030. This extended follow-up is crucial to evaluate the long-term effectiveness of the different screening methods in reducing colorectal cancer-specific mortality. Researchers anticipate that the final evaluation will demonstrate a reduction in mortality from colorectal cancer in the screened groups, and longer-term follow-up is considered crucial to determine the impact on overall cancer prevention. Anna Forsberg, a docent at Karolinska Institutet and last author responsible for SCREESCO, has expressed hope that the final evaluation will show this reduction.