Interval cancers in a guaiac-based colorectal cancer screening programme: Consequences on sensitivity

Area of Science:

• Oncology
• Public Health
• Gastroenterology

Background:

• Population-based colorectal cancer screening programs aim to reduce mortality.
• The Stockholm/Gotland program utilized biennial guaiac-based faecal occult blood tests (Hemoccult®) for individuals aged 60-69.
• Interval cancers, diagnosed between screenings, are crucial for evaluating program effectiveness.

Purpose of the Study:

• To evaluate the rate and characteristics of interval cancers within the Stockholm/Gotland colorectal cancer screening program.
• To assess the sensitivity of the screening test and identify areas for quality improvement.

Main Methods:

• Cross-referencing screening histories with the Swedish cancer register for cancers diagnosed between 2008 and 2012.
• Analyzing data from 203,848 participants invited to screening.
• Calculating test- and episode sensitivities and interval cancer rates.

Main Results:

• Out of 557 colorectal cancers, 39.3% were screen-detected and 60.7% were interval cancers.
• The interval cancer rate was 17.1 per 10,000 tests.
• Screening sensitivity was significantly lower in women (22.4-32.2%) compared to men (43.2-52.0%).
• Program sensitivity and screen-detected cancer rates increased over the study years.

Conclusions:

• Interval cancer rates higher than screen-detected rates suggest the need for more sensitive screening methods.
• Lower screening sensitivity in women warrants further investigation.
• Compliance and quality of follow-up colonoscopies are important factors for program success.