Colorectal Cancer Screening

FAP: annual flex sig beginning at age 10 or 12 yrs; colectomy should be considered when polyposis is detected (in attenuated FAP, annual colonoscopy is required as many polyps will only present in the proximal colon) + upper endoscopy every 1-3 yrs, starting at age 25-35

HNPCC: colonoscopy every 1-2 yrs starting at age 20-25 (or 10 yrs earlier than age of diagnosis for youngest affected family member).  Annual colo after age 40. Consider prophylactic hysterectomy and salpingo-oophorectomy.  Also includes annual screening renal US and urine cytology.

IBD: pts with UC and Chron’s disease have increased risk for colon ca (proportional to duration if disease, extent of colon involvement and coexistence of sclerosing cholangitis).  Screening colonoscopy should be initiated in patients who have had the disease for >8 yrs.  If dysplasia is detected, colectomy should be considered.

Average risk (no family hx of adenomatous polyps or colon ca): starting at age 50; frequency depends of the modality of screening:

• Screening is feasible b/c on average the process of polypàcancer takes 10-15 yrs
• Most screening strategies result in cost-effectiveness ratios of 10-25K per year of life saved
• FOBT (or FIT) requires annual testing with 2 samples collected from 2 separate, spontaneously passed stools (no red meat, asa and certain fruit/veg must be eliminated from diet prior to testing)—if done correctly can reduce colorectal-ca related mortality by 33%
• DRE-obtained FOBT is not acceptable (reduces efficacy five-fold)
• Flexible sigmoidoscopy decreases cancer mortality by 45%; should be performed every 5 yrs if no adenomas detected
• combined FOBT and flex sig increases the detection rate of colon ca to 76%
• Colonoscopy can be diagnostic and therapeutic; studies have found a reduced incidence of colorectal ca of 66-90% but there have been no RCTs that show a reduction in cancer-related mortality (although can likely extrapolate the flex sig data)
• Barium enema no longer recommended for screening
• CT colonography? sensitivity of polyp detection is cariable, radiation exposure, surveillance interval unclear
• Fecal DNA testing? sensitivity varies, no studies demonstrate a mortality benefit

 

(Victoria Kelly MD, 8/31/10)