Colorectal Cancer Screening

1. Colorectal Cancer Screening September 10, 2002 Jorge Garcia, MD

2. What is the risk of getting colon cancer? • Increases steadily with age. • At age 50, annual risk is one in 10,000. • At age 50, lifetime risk is one in 20. Half of these will of die of the cancer. • On average, colon cancer decreases the life expectancy of the “victim” by 13 years.

3. What are the more common ways if dying? • Among 50 year old women...

4. What are the more common ways if dying? • Among 50 year old women… • 1 in 200 will get breast cancer in 10 years. • 1 in 500 will get colon cancer in 10 years. • 1 in 500 will die of heart disease in 10 years. • 1 in 500 will die of an accident in 10 years.

5. What are the more common ways if dying? • Among 50 year old women… • …if she smokes:

6. What are the more common ways if dying? • Among 50 year old women… • …if she smokes: • One in 50 will die of lung cancer in ten years. • One in 77 will die of heart disease.

7. What can prevent colon cancer? • High fiber diet?

8. What can prevent colon cancer? • High fiber diet? Observational studies suggested this might help. • Two recent randomized studies showed no benefit in patients with prior adenomas.

9. What can prevent colon cancer? • Calcium?

10. Calcium, 1200 mg /day • Two recent RCT in patients with prior adenomas. • Both demonstrated reduced risk of recurrence. • NNT: 15 over four years to prevent one adenoma.

11. What can prevent colon cancer? • ?

12. What can prevent colon cancer? • NSAIDs (including COX-2 inhibitors): • Studies only in familial polyposis. • Reduced incidence of polyps only while on the medication. • Unable to generalize to average risk patients.

13. What causes colon cancer in most people? • ?

14. What “causes” colon cancer in most people? • Polyps

15. What causes cancer in most people? • Adenomatous polyps are the problem

16. What causes cancer in most people? • Adenomatous polyps are the problem • …and the solution?

17. Adenomatous Polyps • Cause 80% of CRC. • They grow slowly, undergo malignant transformation. • Over a ten year period? • Or less?

18. Adenomatous Polyps • Frequency of polyps increase with age: • At age 50, 20% of people will have at least one polyp. • At age 60, 40%. • At age 80, >55%. • Most polyps are small: 85% are < 1cm.

19. Big polyps are bad. • If < 1cm, fewer than 1% will become cancer in ten years. • If > 1 cm: • 10% will become malignant in 10 years. • 25% will become malignant in 20 years.

20. Polyps are the solution. • If they “cause” most cancers, finding and deleting them might reduce CRC mortality.

21. How do you find these polyps in time? • ...

22. How do you find these polyps in time? • FOBT • Flexible Sigmoidoscopy • Colonoscopy • Barium enema • Virtual colonoscopy

23. FOBT • Multiple randomized control trials demonstrate reduced mortality from CRC. • Minnesota Colon Cancer Control Study (Mandel 1999, Mandel 2000) showed decreased CRC mortality of 21-33%. • Total mortality in controls: 14/1000. • Total mortality in annual screened: 9.5/1000

24. FOBT • Compliance varies from 50-75%. • Number needed to invite to screening to prevent one colon cancer: 142. • Total increase in life expectancy of screened population: 6 days.

25. PAP Smears • Increase life expectancy in screened populations by 11.6 to 32.4 days… • …and PSA decrease life expectancy in screened populations by one day.

26. FOBT • Rehydrating slides increase sensitivity (40% goes to 60%), • But decreases specificity (97% goes to 90%).

27. FOBT • Annual screening increases yield of positives. • Multiple slides increase yield. • No evidence around changing diet or meds.

28. What does a “positive” FOBT mean for the patient? • ...

29. What does a “positive” FOBT mean for the patient? • 8% of these will have a large polyp or cancer. • 2% will be cancer. • Annual FOBT screening will find 50% of cancers. • Annual FOBT will result in 38% of screened people being “positive” and needing colonoscopy.

30. What about a DRE? • ?

31. What about a DRE? • NO evidence that DREs reliably screen for CRC. • Guiac of stool after DRE is not recommended as a screen for cancer.

32. Flexible Sigmoidoscopy • No randomized control studies on Flex Sigs alone. • Case-control study (Selby) suggest that screened populations have fewer fatal colon cancers that controls. • Flex sig alone would miss proximal cancers: what about combining this with FOBT?

33. FOBT + Flex Sig • Two recent good randomized controlled trials. One cohort study: • Various numbers and protocols, but… • 42% will get colonoscopy in 10 years. • Decreased CRC mortality by 45.6%. • Increased life expectancy for screened population estimated to be 8.5 days (based on 50% compliance).

34. Lieberman, NEJM, July 2001 • 2885 patients • rehydrated FOBT and colonoscopy • 1st 60 cm was used as proxy for Flex Sig. • Found that FOBT + Flex sig would have missed 24% of advanced adenomas (>1cm).

35. Lieberman, NEJM, July 2001 • Raised serious questions about the validity of flex sig screening. • But his study was only a single year of FOBT. Would annual tests have reduced the number of missed adenomas? • Not a screening population, but recruited from families with CRC history.

36. Colonoscopy • Medicare started paying for screening colonoscopies this year.

37. Colonoscopy • No randomized controlled trials of screening. • A single case-control study suggested lower CRC mortality (odds ratio = 0.42). • Several strategies proposed: once in a life time, twice in a life time, every ten years.

38. Double Contrast BE • No randomized controlled trials. • National Polyp Study, only 48% of polyps greater that 1cm were found. • Specificity also low, at 85%.

39. Virtual Colonoscopy • “CT Colography” • Complete bowel prep, same as with colonoscopy. • Fill colon with air through a rectal tube. • After the CT, perform post image processing and review by radiologist. • Experimental. • Can’t see flat polyps or lesions.

40. Harms of screening • False positives from FOBT and Flex Sigs: • anxiety • cost • loss of time due to work up • complications of colonoscopy...

41. Harms of screening • Sigmoidoscopy: Bowel perf 1/10,000. • Colonoscopy: Conscious sedation risk? • Published complication rate of colonoscopy • Bleed requiring hospitalization: 1/500 • Perforation: 1/750 • Serious morbidity (CVA, etc.) 1/800 • Die: 1/8000

42. USPSTF recommendations • Begin screening for CRC at age 50. • “Periodic” FOBT (good evidence) • Flex sig ( fair evidence) • No evidence (yet?) for screening colonoscopy.

43. My recommendation: • Annual rehydrated FOBT age 50 - 70 • Flex sig q 5 years if FOBT negative. • Refer any +hemoccult and any polyp on FS to colonoscopy. • Consider primary colonoscopy at age 50 and 60 if sedation would be useful, and if unable to comply with FOBT.

44. High Risk Populations: the other 20% of colon cancers... • Family Hx of CRC: • One 1st degree relative with Dx at age <60. • 2 or more 1st degree relative at any age. • May have hereditary non-polyposis colon cancer syndrome.

45. High risk patients: • Known family or personal history of adenomatous polyposis. • Ulcerative colitis present for >8 years. • Crohn’s disease. • Prior colon cancer or adenomatous polyp.

46. High risk patient management: • Consult GI: • Consider colonoscopy at frequent interval, at least q 5 years.