Colorectal Cancer Screening

Introduction

Colorectal cancer screening is crucial for early detection and prevention, with various guidelines recommending different screening intervals and methods based on individual risk factors, as supported by the American College of Gastroenterology, American Cancer Society, US Preventive Services Task Force, US Multi-Society Task Force, and NCCN Guidelines 1, 2, 3, 4, 5, 6, 7, 8, 9, 10

For average-risk patients, both CT colonography and optical colonoscopy are appropriate screening methods for colorectal cancer, with optical colonoscopy being preferred due to its ability to both detect and remove polyps in a single procedure, as recommended by the American College of Radiology and the American College of Internal Medicine 10, 11
Optical colonoscopy has a higher risk of complications, with a perforation rate of 1 in 1,000, compared to CT colonography, which has a perforation rate of 1 in 22,000 11
CT colonography detected 90% of patients with large (≥10 mm) adenomas and cancers, according to the American College of Radiology Imaging Network (ACRIN) National CT Colonography Trial 12, 11
The sensitivity and specificity of different screening tests are as follows:
Test Sensitivity for CRC Sensitivity for Advanced Precancerous Lesions Specificity
Cologuard 92.3% 42.4% 86.6%
FIT 73.8% 23.8% 94.9%
5, 1

Test	Sensitivity for CRC	Sensitivity for Advanced Precancerous Lesions	Specificity
Cologuard	92.3%	42.4%	86.6%
FIT	73.8%	23.8%	94.9%

Per-polyp sensitivity for large adenomas and cancers was 84% for CT colonography 11
Per-patient sensitivity for detecting adenomas ≥6 mm was 78% for CT colonography 11
Similar detection rates were found for CT colonography and colonoscopy in parallel screening programs, with some studies showing CT colonography sensitivities of 94% compared to 88% for colonoscopy in detecting adenomatous polyps ≥10 mm 11

Optical colonoscopy is the preferred screening method for high-risk patients, including those with family history of colorectal cancer, hereditary syndromes, inflammatory bowel disease, and previous adenomatous polyps, as recommended by the American College of Internal Medicine and the American College of Radiology 10, 11
Average-risk individuals should start screening at 45 years, as recommended by the American College of Gastroenterology, American Cancer Society, US Preventive Services Task Force, US Multi-Society Task Force, and NCCN Guidelines, with a qualified recommendation, Grade B recommendation, weak recommendation, and strong evidence, respectively 3, 4, 5, 6, 7, 8
African Americans should start screening at 45 years, although some guidelines suggest starting at 40 years, as recommended by the American College of Physicians, American College of Gastroenterology, and US Multi-Society Task Force 3, 4, 10
The recommended screening intervals are as follows:
Screening Test Interval
Colonoscopy every 10 years
FIT annually
FIT-fecal DNA (Cologuard) every 3 years
CT colonography every 5 years
Flexible sigmoidoscopy every 5 years
5, 2
A 10-year screening interval is recommended if the colonoscopy results are normal, reducing the need for frequent testing 13

African American race is associated with an earlier mean age at onset of colorectal cancer, and has the highest incidence and mortality rates for colorectal cancer compared to other racial/ethnic groups (43.6 cases per 100,000 vs. 37.8 cases per 100,000 in White adults) 4, 1
A 20-pack-year smoking history is a significant risk factor for colorectal cancer 4
Individuals with a family history of colorectal cancer should start colonoscopy at age 40 or 10 years before the youngest affected relative's diagnosis, and repeat every 5 years if there is one first-degree relative diagnosed with CRC or advanced adenoma before age 60 1
For patients with Familial Adenomatous Polyposis (FAP), endoscopic surveillance should begin at puberty, and consider genetic testing and colectomy if positive, based on moderate-strength evidence 9
For patients with Inflammatory Bowel Disease, colonoscopy should begin 8 years after onset of pancolitis or 12-15 years after onset of left-sided colitis, and repeat every 1-2 years, based on moderate-strength evidence 9

Adenomatous polyps found and removed should be followed up with colonoscopy in 3-5 years, depending on the size and number of polyps 5
Any positive Cologuard test should be followed up with a diagnostic colonoscopy, and a positive stool-based test should be followed up with timely colonoscopy 5, 2

Screening should continue through age 75 for average-risk adults in good health with life expectancy >10 years, as recommended by the American Cancer Society 5
For individuals aged 76-85, the decision to continue screening should be based on prior screening history, overall health status, life expectancy, and patient preferences, as recommended by the US Multi-Society Task Force and US Preventive Services Task Force 4, 6
Screening should be discontinued after age 85, as the overall mortality risk and adverse events associated with follow-up colonoscopy outweigh potential benefits, as recommended by the US Multi-Society Task Force, American Cancer Society, and NCCN Guidelines 5, 6, 7
The American College of Physicians recommends discontinuing screening for adults with a life expectancy of less than 10 years, based on moderate-strength evidence 10

Patient preferences should be considered when selecting screening tests to improve adherence 10
Potential harms of screening tests should be considered, including colonoscopy (small risk of perforation and bleeding), CT colonography (radiation exposure), and stool-based tests (false positives leading to unnecessary follow-up procedures) 14, 15, 10
Assessing risk factors for each cancer type, determining appropriate starting age based on risk profile, presenting appropriate screening options based on guidelines, considering patient preferences and barriers to adherence, implementing screening schedule with appropriate follow-up and surveillance, and reassessing periodically based on new findings and updated guidelines are all crucial steps in cancer screening, as supported by the American Cancer Society 5