COLORECTAL CANCER SCREENING in December of 2002 Jeffrey W. Frank, MD

Colon Cancer Screening Why Screen? 2nd leading cause of cancer deaths in the USA 1 in 20 over the age of 50 will develop colorectal cancer in lifetime Pre-malignant lesion - the adenomatous polyp Removal of adenomas prevents cancer Established cancer generally progresses slowly and early stages are curable

COLORECTAL NEOPLASIA Adenoma/Carcinoma Sequence Normal Epithelium Hyperproliferative Epithelium ADENOMA CARCINOMA 2. APC (both alleles) Kras DCC p53 (17p) METASTASIS other factors 1. Mismatch repair genes (HNPCC)

COLORECTAL NEOPLASIA Distribution 50% 15% 35% 50% 10% 15% 25% ADENOMASCARCINOMAS

Colorectal Cancer Screening Who should be screened? Symptomatic Asymptomatic Race High risk groups Gender Distal adenomas AGE most important

Colorectal Cancer Screening Age - the most important factor 90% of colon cancer in age >50 Benign adenomas are more prevalent after age 50 and especially after age 60 Chances of finding a polyp is about 25% Proximal colon cancers increase with age

Age and Colorectal Cancer Colon CancerAdenomas Winawer SJ. Gastro 1997

Colorectal Cancer Screening Do distal polyps predict proximal polyps? Patients who have distal adenomas have a 3-6% chance of having a significant proximal adenoma >2/3 of patients with proximal cancer will not have a distal polyp Therefore, distal adenomas are insensitive markers for proximal lesions and proximal lesions are unassociated with distal lesions Schoen RE, Gastro 1998 Rex DK, Gastroentest Endosc 1999

COLORECTAL NEOPLASIA Pathologic Subtypes Probability of Malignancy

COLORECTAL NEOPLASIA Heritability 80% sporadic; 20% genetic Of genetic Cancers: – 1% FAP – 6% HNPCC – 10-15% familial Lifetime risk: – Average American- 6% – One 1st degree relative > % – One 1st degree relative < % Two 1st degree relatives - 34% One 2nd degree relative - 9% One 3rd degree relative - 7% Average risk Ashkenazic Jew - 9% Ashkenazic Jew with FH and APC gene mutation - 28% Women with h/o Breast or Genital cancer - 10%

HNPCCHNPCC Amsterdam Criteria-II – 3 or more relatives with a histologically verified HNPCC-associated cancer (colorectal, endometrial, small bowel, ureter or renal pelvis), one of whom is a first-degree relative of the other two; AND – Colorectal cancer involving at least two generations; AND – One or more colorectal cancer cases diagnosed before the age of 50

COLORECTAL NEOPLASIA Associations Risk Factors: – high serum cholesterol – high saturated fat diet – high “red” meat diet – increased bowel anerobic flora – increased colon pH – low fiber diet – obesity – smoking

COLORECTAL NEOPLASIA Chemoprevention ?Fiber Low red meat (animal fat) Folic acid Calcium/vitamin D Selenium Omega-3 fatty acids ?NSAIDs

Screening Populations for Colorectal Cancer Obstacles Nonparticipation – estimated 50% of population to be screened will not participate Screening insensitivity – FOBT miss rate ~ 70% Incomplete colorectal evaluation – estimated 33% with positive FOBT will not undergo complete evaluation Old Age – ~20% of colorectal cancers are found in patients older than age 80 – detecting asymptomatic cancers may not benefit them Advanced Stage – estimated 25% of asymptomatic cancers are stage C or D Lead-Time Artifact – estimated 50% of asymptomatic cancers remain stage A or B when symptoms develop Screen-Related Mortality – false negatives with false reassurance, delayed diagnosis – false positives subject to anxiety, lost work days, procedure morbidity and mortality

FOBT in a Simulated Population at Moderate Risk for Colorectal Cancer Adapted from Ahlquist DA, Cancer (Supplement), 1992 Assumed target population of 20,000 persons 50 yrs or older. At expected prevalence of 0.5%, an estimated 100 colorectal cancers would be present at the time of screening

Colorectal Cancer Screening Methods of Screening Tests of Fecal Occult Blood Digital rectal exam Flexible Sigmoidoscopy Barium Enema (SCBE vs DCBE) Colonoscopy “Virtual Colonoscopy”

Tests of Fecal Occult Blood False Positives Occur - Specificity 90-98% (2-10% false positive) – many lesions bleed – dietary factors False Negatives Occur - Sensitivity 38-92% (high false negative rate) – not all cancers bleed – reducing substances false neg (Vitamin C)

Tests of Fecal Occult Blood Annual FOBT reduces mortality from CRC by 15-33% in randomized, controlled trials Tends to detect earlier stage cancers FOBT is insensitive for polyps Poor patient compliance Diagnostic follow-up is required and compliance with this is poor

Colorectal Cancer Screening Flexible Sigmoidoscopy Widely available Simple preparation/no sedation Minimal risk Relatively inexpensive Sensitive for polyp detection in visualized colon Biopsy possible Poor compliance Prep often inadequate At best, 1/3 of colon visualized so 1/2 of colon cancers missed “Like a mammogram of one breast” Full colonoscopy required if polyps found ProsCons

Colorectal Cancer Screening Flexible Sigmoidoscopy Few prospective studies Flex sig and FOBT fails to detect 24% of advanced neoplasia Leiberman et al NEJM 2001 Case control studies (predominantly of rigid sigmoidoscopy) show a 60% reduction in mortality from CRC in part of colon examined Addition of FOBT to sigmoidoscopy may reduce mortality by an additional 50%

Colorectal Cancer Screening Barium Enema No prospective or cohort trial for CRC screening Double contrast better than single DCBE is 50-80% sensitive for polyps 1 cm; 55-85% for stage I and II cancer Insensitive in rectosigmoid area (missed 25% of cancers in pts with positive FOBT) Anecdotally less comfortable than colonoscopy Abnormalities detected require colonoscopy Kewenter J. Endoscopy 1995

Colorectal Cancer Screening Colonoscopy No prospective trials for CRC screening and mortality – Sigmoidoscopy and polypectomy reduce CRC mortality – Nat’l polyp study cleared the colon of adenomas in high risk pts and there was a 76-90% reduction in CRC and no deaths – Colonoscopy screening studies show a prevalence of polyps twice that of flexible sigmoidoscopy

Colorectal Cancer Screening Colonoscopy Evaluates entire colon Allows diagnosis and treatment of lesions found More sensitive than FOBT or sigmoidoscopy Theoretically prevents colon cancer Operator dependent Expensive Difficult preparation Poor compliance Uncomfortable, embarrassing Potentially risky Incomplete exam in 5-20% Polyps can be missed Operator dependent Expensive Difficult preparation Poor compliance Uncomfortable, embarrassing Potentially risky Incomplete exam in 5-20% Polyps can be missed ProsCons

Colorectal Cancer Screening “Virtual Colonoscopy” Uses spiral CT technology Bowel preparation required Sensitivity for polyps >1 cm – 75% - 93% (<1cm 19-82%) Specificity – 90% - 100% Time will tell if improves patient compliance for screening Colonoscopy still needed to remove polyps ? Cost-effective at this time

Colorectal Cancer Screening Recommendations Annual FOBT and Flexible Sigmoidoscopy every 5 years DCBE every 5 to 10 years Colonoscopy every 10 years Average Risk Persons over age 50

Colorectal Cancer Screening The Future A test that detects “significant adenomas” Non-invasive test of stool or preferably blood or saliva Better tolerated colon preparation