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 JTMIRO@UQU.EDU.SA