What are the Australian guidelines for colorectal cancer screening?

Australian Guidelines for Colorectal Cancer Screening

The Australian National Bowel Cancer Screening Program (NBCSP) recommends biennial immunochemical faecal occult blood test (iFOBT) screening for average-risk individuals aged 50-74 years as the primary colorectal cancer screening strategy. 1, 2

Risk Categorization and Screening Recommendations

Category 1: Near Average Risk (No or Weak Family History)

• Biennial iFOBT screening from age 50 to 74 years 1
• This is the approach implemented in the National Bowel Cancer Screening Program 2
• This strategy is highly cost-effective with an incremental cost-effectiveness ratio of A$2,984-5,981 per life-year saved depending on adherence 2, 3

Category 2: Moderate Risk (Family History)

• Biennial iFOBT from age 40 to 49 years 1
• Colonoscopy every 5 years from age 50 to 74 years 1
• Moderate risk is defined by specific family history criteria (multiple affected relatives or diagnosis at younger age) 1

Category 3: High Risk (Strong Family History)

• Biennial iFOBT from age 35 to 44 years 1
• Colonoscopy every 5 years from age 45 to 74 years 1
• Genetic syndromes have been removed from this category in the 2017 revised guidelines 1

Screening Test Options

For average-risk individuals (Category 1), the following screening options are available:

• Recommended Primary Test: Biennial iFOBT (immunochemical Faecal Occult Blood Test) 1, 2
• Alternative options that have been evaluated but are not part of the national program include:
  • Flexible sigmoidoscopy every 5 years 4
  • Colonoscopy every 10 years 4
  • CT colonography every 5 years 4
  • Faecal DNA testing 4

Benefits of the Current NBCSP Approach

• The fully implemented NBCSP with biennial iFOBT screening is expected to reduce colorectal cancer incidence by 23-51% and mortality by 36-74% compared to no screening (range depends on participation rates) 3
• FOBT screen-detected cancers show favorable characteristics including earlier stage at diagnosis and superior relapse-free and overall survival compared to non-screen-detected cancers 5
• The number-needed-to-colonoscope to prevent one death is 35-49 with the current program 3

Considerations for Age Extensions

• Starting screening at age 45 years could be cost-effective but would:
  • Increase colonoscopy demand by 3-14% 3
  • Require 55-170 additional colonoscopies per additional death prevented 3
  • Have a less favorable incremental benefits-to-harms trade-off than the current 50-74 years approach 3

Implementation Challenges

• Current participation rates in the NBCSP are around 40%, well below optimal levels 3
• Uptake is lower among high-risk groups including those with obesity, high alcohol consumption, and current smokers 6
• General practitioners can play an important role in improving participation in the national program 6

Recent Updates

The 2017 revised Australian guidelines made several changes from the 2005 version:

• Minor changes to family history inclusion criteria for categories 1 and 2 1
• Genetic syndromes removed from category 3 1
• Introduction of initial iFOBT screening before transitioning to colonoscopy for categories 2 and 3 1

The current evidence supports maintaining the NBCSP's approach of biennial iFOBT screening for average-risk individuals aged 50-74 years as the most cost-effective and practical population-based screening strategy 2, 3.