What are the Canadian screening guidelines for Fecal Immunochemical Test (FIT) testing for colorectal cancer?

Canadian FIT Screening Guidelines for Colorectal Cancer

The Canadian Task Force on Preventive Health Care (CTFPHC) recommends fecal occult blood testing (either guaiac-based or FIT) every 2 years for average-risk adults aged 50-74 years, and does NOT recommend colonoscopy as a primary screening test in Canada. 1

Screening Age and Population

• Start screening at age 50 for average-risk individuals 1
• Stop screening at age 75 - do not screen individuals 75 years or older 1
• These recommendations apply to asymptomatic adults with no family history of colorectal cancer and no prior screening 2

FIT Testing Specifications

The Canadian approach differs significantly from U.S. guidelines in two key ways:

• Screening interval: Every 2 years (not annually as recommended in the U.S.) 1
• Colonoscopy is NOT recommended as a primary screening test in Canada, largely due to limited access and resource constraints 1

Technical Details from Provincial Programs

• Canadian provincial programs use either guaiac-based fecal occult blood tests or fecal immunochemical tests 3
• When FIT is used, quantitative tests are preferred over qualitative tests 1
• Lower threshold cut-offs (20 μg/g or lower) are favored to define a positive test 1
• Single-sample FIT collection is the standard approach 3

Follow-up of Positive Results

When FIT is positive, colonoscopy is the mandatory next step 1

• Target: 80% of individuals with positive FIT should complete colonoscopy within 180 days 3
• Current Canadian performance shows 80.5% uptake of colonoscopy within 180 days after abnormal FIT, ranging from 67.8% to 89.5% by province 3
• Delays beyond 6 months after positive FIT significantly increase risk: adjusted OR 1.31 for any colorectal cancer and 2.09 for advanced stage disease 4

Performance Metrics from Canadian Programs

Real-world data from five Canadian provincial programs (2009-2011) demonstrates:

• Positive predictive value for adenoma: 35.9% for guaiac-based tests and 50.6% for FIT 3
• Adenoma detection rate: 16.9 per 1000 screened 3
• Cancer detection rate: 1.8 per 1000 screened 3
• Of invasive cancers detected, 64.6% were stage I or II 3
• Overall positivity rate: 4.4% 3

Critical Differences from U.S. Guidelines

The Canadian approach is more conservative than recent U.S. recommendations:

• U.S. guidelines now recommend starting at age 45 (American Cancer Society 2018, USPSTF 2021), while Canada maintains age 50 1, 5
• U.S. recommends annual FIT, while Canada recommends biennial testing 1
• U.S. includes colonoscopy as a tier 1 screening option, while Canada does not recommend it as a primary screening test 1

The rationale for biennial (every 2 years) rather than annual screening:

• Most RCT data examined biennial screening with fecal occult blood tests 1
• A large U.S. study found no significant difference between annual and biennial screening in overall or cumulative colorectal cancer mortality through 30 years of follow-up 1
• Biennial screening reduces harms and burden while achieving similar mortality reduction 1

Emerging Considerations

Recent evidence suggests Canadian guidelines may need updating:

• Colorectal cancer incidence is rising in Canadians under age 50, similar to U.S. trends 5
• Modeling studies suggest FIT screening starting at age 45 would reduce incidence by 103 per 100,000 and deaths by 43 per 100,000, with an incremental cost-effectiveness ratio of $5,850 per QALY 6
• FIT screening at age 40 would reduce incidence by 161 per 100,000 and deaths by 71 per 100,000, with an ICER of $7,038 per QALY 6
• However, official Canadian guidelines have not yet been revised to reflect these findings 5

Common Pitfalls

• Do not perform upper gastrointestinal evaluation for a positive FIT with negative colonoscopy in the absence of upper GI symptoms 1
• Do not use dietary restrictions - patients should be explicitly instructed they do not need to adjust diet or medications to complete FIT 1
• Do not use digital rectal exam samples - FIT programs should rely on spontaneously passed stool specimens 1
• System barriers are the primary cause of non-adherence, including failure to arrange colonoscopy, failure to inform patients of positive results, and inadequate patient contact 4