Colon Cancer Screening and Prevention
DR Jameel Tariq Miro
Colorectal Cancer
Lifetime incidence 5%90% of cases occur after age 50One-third of patients with colorectal
cancer die from the diseaseOnly approximately 50 % of patients
are screened for colorectal cancer
Colorectal cancer is a preventable disease
Colon polyps
Two-thirds of polyps are adenomas (dysplasia)
Adenoma prevalence 25% at age 50 and 50% by age 70
Risk of cancer increases with polyp size, number, and histology
The polyp examined is representative of the individual’s propensity to form
polyps and cancer
Colon Cancer Screening – When to Begin?
Average risk – begin at age 50Family risk factors
Primary degree relative doubles riskBegin screening at age 40 or 10 years earlier
than diagnosis of relativeColon cancer syndromes (5-10% of colon
CA)Hereditary non-polyposis colorectal cancer
(HNPCC)*▪Colonoscopy every 1-2 years beginning at age 20-25
Familial Adenomatous Polyposis (FAP)
CRC Screening Guidelines- Average Risk
GI ConsortiumAnnual FOBTFlex sig every 5 yrsCombination of
aboveDCBE every 5
yearsColonoscopy every
10 years (preferred option – ACG)
American Cancer Society
Recommendations now identical to the GI
consortium
Quantitative immunochemical FOBT
Improved detection of hemoglobin as compared to guaic based FOBT tests
Immunochemical FOBT testing uses antibodies to human globin expressed in colorectal
bleeding .94 % sensitivity for cancers and 67 % for
advanced adenomas with approximate 90% sensitivity in high risk individuals
Has not yet been tested in asymptomatic average risk patients
A word about the digital rectal exam
Sigmoidoscopy Weaknesses
20-30 % of proximal advanced adenomas are missed with
sigmoidoscopySigmoidoscopy particularly poor in
women missing 65 % of advanced polyps as opposed to colonoscopy
(NEJM 2005)
Would you ever mammogram one breast?
Screening Colonoscopy
Two large cohort studies (Winawer, et al, NEJM 1993 and Citarda, et al Gut 2001)
have demonstrated significant reductions in colon cancer incidence if colonoscopy
with polypectomy are performed
FOBT and sigmoidoscopy that lead to colonoscopy with polypectomy have been
shown to significantly reduce colorectal cancer mortality
Screening colonoscopy
Combines the most complete examination of the colon with the
direct therapy of removing dysplastic polyps
The role of polyps as a precursor to cancer provides the rationale for
endoscopic screening illustrated by the benefit of adenoma removal by
polypectomy at the time of colonoscopy
Novel and Emerging Advances in Colorectal Cancer Screening
CT colonography/Virtual colonoscopyFecal DNA analysisCapsule endoscopy
CT colonography/Virtual colonoscopy
Computed tomography procedure that uses helical, multiple thin
section images along with specialized computer programming
to provide three-dimensional and two-dimensional images of the colon
Can you tell the difference between these polyps?
Fecal DNA Analysis
Colorectal cancer is a disease in which many DNA mutations associated with
carcinogenesis have been characterizedStool DNA is stable, shed continuously and
through amplification tests can be detected in minute amounts
Most studied stool test for DNA mutations is a multicomponent test that targets
point mutations at 15 “hot spots” on K-ras, APC, p53, Bat-26, and long DNA
Fecal DNA Analysis
Alquist, et al. Gastroenterology 2000 studied patients with colon cancers, large adenomas, and normal colons
Sensitivity of 91% for colon cancer, 82% for large adenomas and a specificity of
93%Imperiale, et al. NEJM 2004 studied
patients in a screening populationPoor sensitivity for invasive cancers
(52%) and advanced polyps (15%)
M2A® Capsule Endoscope
• M2A captures images at 2 fps
• More than 50,000 images are taken
• Field of view: 140º
• Min. detectable object: Less than 0.1 mm
Mouth to Cecum
Teeth Epiglottis
Small Intestine Ileocecal valve Wall of right colon
Multiple telangiectasia on a gastric fold
Summary – Colon Cancer Screening
FOBT, barium enema, sigmoidoscopyAll recommended but all with significant weaknessesWill iFOBT make a come back?
Screening ColonoscopyStandard of care – Diagnosis along with therapy
CT colonographyHere today – Further verification using one
technology in multicenter study and more importantly how CT colongraphy will work with
standard colonoscopyFecal DNA analysis and Capsule Endoscopy
Here tomorrow – Further refinement and technical improvements needed
THANK YOU [email protected]