Other topics in Screening

1
The Colon....last 5 parts of gastrointestinal
tract
Transverse colon
5
Ascending Colon
Descending colon
9
flow from upper GI tract
16
ileum
Cecum
20
50
Sigmoid colon
Rectum
appendix
2
Colorectal Cancer Screening

• 1993 152,000 new cases 57,000 deaths
• Natural hx
• begins with adenomatous polyp
• most polyps are benign
• occasional polyp becomes malignant (proportion?
  1/10? in older people polyps more common)
• age-related disease -- incidence increases
  dramatically at about age 50

3

• Higher proportion of cancers near distal
  colon/rectum
• 20 in first 20 cm
• 40 in next 40 cm
• 40 spread thru rest to illeum
• Staging
• Dukes A, B, C, D
• probably slow progression through the stages
• survival drops drastically for those found in C
  or D stage

Note these differ from first slides...
4
Screening tests that have been suggested

• FOBT (guaiac testing) (Minnesota study)
• Digital rectal exam
• Barium enema
• Sigmoidoscopy (flexible) (Kaiser-Perm.)
• Colonoscopy
• Lately
• helical CT for computed tomographic
  colonography
• 3D reconstructed helical CT - virtual
  colonoscopy
• genetic test ... pcr amplifies genes in cells
  shed by an active colon cancer

5
The Colon....last 5 parts of gastrointestinal
tract
Transverse colon
5
FOBT, colonoscopy, imaging tests
Ascending Colon
Descending colon
9
16
ileum
20
50
6
Colorectal Ca Screening

• RCT showed FOBT reduced 13 year mortality by
  30.
• absolute 13-yr mortality went from 0.9 to 0.6
• Average 50 year old about 5 risk of having
  colon ca by age 80 2.5 chance of dying from it.

7

• Screening is expensive -- several billion per
  year (although estimates of /QALY from a few
  years ago put it under 50K/QALY, recent modeling
  shows lowest at about 90K/QALY)
• The REAL expensive part is surveillance post
  polypectomy
• examine q 3 y with colonoscopy is VERY expensive
• nowhere has a surveillance protocol been examined
  for its costs and effectiveness.
• What will you recommend to your patient
  population? and Why?
• see clinical debate, 34(f) vol. 1, p. 449 ff

8
This week in NEJM
20 min. video tape on colon cancer screening
trials then discussion
9
Most recent analysisFrazier, Colditz, Fuchs,
Kuntz. Cost effectiveness of screening for
colorectal cancer in the general population.
JAMA 2000 (Oct 18) 2841954-1961.
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