Colorectal Cancer Screening in Average Risk Populations: Evidence Summary

Guideline Objective

The purpose of this systematic review is to evaluate the existing evidence concerning screening of adults at average risk for CRC in the context of an organized, population-based screening program. The main objectives are to identify:

• The benefits and harms of screening in this population;
• The optimal primary CRC screening test(s) for this population;
• The appropriate ages of initiation and cessation for screening in this population; and
• The intervals at which people at average risk should be recalled for CRC screening.

Patient Population

Adults at average risk for colorectal cancer.

Intended Guideline Users

Primary care providers, endoscopists, policy-makers, and program planners in Ontario.

Research Question(s)

1. How do different screening tests, individually or in combination, perform in average-risk people in preventing CRC-related mortality or all-cause mortality or in decreasing the incidence of CRC? Secondary outcomes include the detection of cancer or its precursors, screening participation rate, adverse effects of tests, and test characteristics, such as sensitivity, specificity, positive predictive value, negative predictive value, and proportion of false-positives or of false-negatives.

Secondary Research Questions:

1. What are the appropriate ages of initiation and cessation for screening in people at average risk for CRC? Is there a relationship between age and the effectiveness of CRC screening?
2. What are the appropriate intervals between CRC screening tests (by test)? Is there a relationship between screening intervals and the effectiveness and risks of screening?