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Colorectal cancer screening

Four procedures in use: fecal occult blood test, sigmoidoscopy, colonoscopy and contrast barium enema.

For the general population age 50 years is the age recommended for screening to begin.

ACS now recommending screening begin at age 45 because colorectal cancer recently has been developing in younger aged patients.

Estimated that screening may reduce mortality from CRC by 40%.

By detecting Colorectal Cancer had a curable stage mortality can be reduced: patients with localized Colorectal Cancer have a 90% relative five-year survival, whereas rates for those with regional and distant  disease is 71% and 14%, respectively demonstrating that earlier diagnosis can have a large impact on survival.

It is estimated that 52,000 people in the United States die each year of colon cancer, a preventable disease.
Study models just suggest that approximately 65% of colorectal cancer deaths can be attributed to the lack of adherence with current screening recommendations.
Screening tests can be categorized into invasive and noninvasive modalities.
Invasive modalities include colonoscopy, sigmoidoscopy, capsule colonoscopy, and CT colonography.
Capsule colonoscopy is for patients who have undergone previous incomplete colonoscopies requiring proximal colon imaging and in patients who are at higher risk of colonoscopy or sedation.
A limitation of capsule colonoscopy screening is that it requires extensive bowel preparation to be able to evaluate the mucosa completely.
Risks of capsule colonoscopy are few but include the risk of bowel preparation and electrolyte abnormalities, choking on the capsule, aspiration of the capsule, and the development of retained capsule due to narrowing anywhere in the gastrointestinal tract.
Noninvasive testing options include stool guaiac fecal occult blood test, fecal immunochemical testing, and stool DNA testing.
Biomarker based methods have advantages of a classical screening modalities of imaging and endoscopy.
Genomic biomarkers can identify colorectal neoplasia with significant sensitivity.
The most sensitive FDA approved noninvasive screening test for colorectal cancer is the mt-sDNA test (Cologuard): 92% sensitivity for colorectal cancer in patients 50 years and older, and 42% for advanced adenomas.
The sensitivity for detecting advanced colorectal cancer is 94% and for detecting advanced adenomas was  46% in a trial for mt-sRNA stool testing.

Prevention consists of periodic screening for pre-cancerous polyps with either a colonoscopy or a high sensitive stool-based test.

Sigmoidoscopy associated with reduced incidence and mortality from left-sided but not right sided cancers.

Colonoscopy is the  predominant procedure for screening, its justification is still largely  theoretical as yielding a  greater detection of adenomatous polyps.

Colonoscopy is associated with a 40 to 69% decrease in the incidence of colorectal cancer and a 29 to 88% decrease in the risk of death from this cancer.

In a case controlled study from Canada colonoscopy was associated with a reduction in colorectal cancer mortality, but this reduction was limited to left-sided cancers with no reduction in right side cancers ( Baxter  NN).

Observational studies indicated the association between colonoscopy and reduce colorectal cancer risk is limited to the distal colon: colonoscopy has therefore not yet been proven to be more effective than sigmoidoscopy (Brenner  H,  Singh H).

For high risk individuals age 40 is the age generally recommended for the starting age for screening.

Studies suggest African-Americans should begin screening at age 45 years.

Can decrease incidence of colorectal cancer and death owing to detection of precancerous lesions and malignancies at early stage.

Colonoscopy primary screening tool for colon cancer performed every 10 years beginning at age 50 years in average risk patients and at 40 years for populations at increased risk.

Current guidelines support lowering the age of screening in individuals with a family history of CRC to 10 years younger than the age of diagnosis of the family member or 40 years of age, whichever is lower.

Prevalence of advanced cancer detected during colonoscopic screening higher among men than women.

In a study of 50,148 the male sex was an independent predictor of advanced cancer (Regula).

Cost per year of a life saved about $50,000.

Screening for colorectal cancer (CRC) should begin at age 45 years instead of 50 years, as recommended in the current guideline, the US Preventive Services Task Force (USPSTF).

 

The recommendation is that all adults aged 45 to 75 years be screened for CRC.

U.S. Preventative Task Force (USPTF) recommended screening should stop at age 75 years.

In analysis of 56,374 participants enrolled in the Nurses Health Study and the Health Professionals follow up study CRC screening, found mortality  benefits of screening beyond age 75 patients  in good health may be warranted.

Multitarget DNA testing in asymptomatic persons at average risk for colorectal cancer detects significantly more cancers than fecal immunochemical tests (FIT), but had more false positives (Imperiale TFAS et al).

DNA test includes molecular assays for KRAS mutations, aberrant ND RG4 and BMP3 methylation, and B-actin plus a hemoglobin immunoassay.

In the above study the sensitivity for detecting colorectal cancer was 92.3% with DNA TESTING VS 73.8% for FIT.

In the above study the sensitivity for detecting advanced precancerous lesions was 42.4% with DNA testing and 23.8% with FIT.

The rate of detection of polyps with high-grade dysplasia was 69.2% with DNA testing and 46.2% withFIT.

The number of persons who would be screened to detect one cancer was 154 with colonoscopy, 166 with DNA testing and 280 with FIT.

The USPSTF guidelines recommend against screening patients older than 85 years.
The lag time for benefit from screening for colorectal cancer is approximately 10 years, and if a patient’s life expectancy is estimated to be less than 10 years, screening for colorectal cancer would be unlikely to provide a mortality benefit to the patient.
Modern studies suggest colonoscopy among individuals older than 75 years is associated with the lower risk of colorectal cancer incidence and colorectal cancer mortality and supports the notion that continuation of screening after 75 years of age among individuals without significant comorbidities.
In a study of 84,585 healthy people age 55 to 64 years a single colon colonoscopy screening compared to no screening or a usual care group found an 18% reduce risk of colorectal cancer but at 10 years did not significantly reduce cancer related deaths.

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