1. Cancer Screening
Saving Lives and Healthcare Costs
Dr Wong Nan Soon
Consultant Medical Oncologist
Oncocare Cancer Centre
Mt Elizabeth Medical Centre
Adjunct Associate Professor
Department of Clinical Sciences
Duke-NUS

2. Avoid Overzealous Screening!

3. Message
• Cancer is the commonest cause of death in
Singapore
• Cancer incidence increases with age
BUT
• Effective cancer screening is available for
common malignancies
• Cancer awareness and compliance with
screening recommendations can contribute to
healthy aging workforce

4. Scope
• Biology of cancer
• Cancer epidemiology in Singapore
• Principles behind screening
• Details of screening tests available

5. What Exactly is Cancer?
Hanahan and Weinberg. Cell 2011

6. Stepwise Progression of Cancer
Dynamics of Cancer: Incidence, Inheritance, and Evolution. Frank SA.Princeton (NJ):
Princeton University Press; 2007.
Vogelstein et al.,New Engl J Med 1988

7. Cancer: Top Killer in Singapore
Ministry of Health: Statistics

8. Cancer Burden
Singapore Cancer Registry Interim Report 2005-2009

9. Common Cancers by Gender
Singapore Cancer Registry Interim Report 2005-2009

10. Age Specific Cancer Incidence
Singapore Cancer Registry Interim Report 2005-2009

11. What is Prevention
• Primary prevention
– Prevents onset of disease
– Removes risk factors eg smoking cessation, avoiding
HRT
• Secondary
– Detects disease at early asymptomatic stage
– Stops disease progression
– Eg screening for breast cancer, colon cancer
• Tertiary
– Prevents disease deterioration and complications
– Eg lowering glucose in known diabetic

12. What is Screening
• Detection of unrecognized risk factor or
disease in well patients
• Can be part of primary or secondary
prevention
• Involves clinical examination, blood tests,
procedures such as mammography,
colonoscopy

13. Should We Screen Everyone for Every
Disease?
• Incidence of disease
• Morbidity and mortality of disease
• Is primary prevention possible
• Is early intervention effective/ curative
• Performance of screening test
– Specificity and sensitivity
– Safety, side effects, acceptability
– Cost

14. Evaluating Screening Test
Avoiding Bias
• Screen detected cancers
vs symptomatic cancers
– Lead time bias
– Length time bias
– Overdiagnosis bias
– Selection bias

15. Recommended Screening
Cancer Type Average Risk High Risk
Breast cancer Yes Yes
Colorectal cancer Yes Yes
Cervical cancer Yes Yes
Ovarian cancer No Yes (BRCA mutation)
Uterine cancer No Yes (Lynch syndrome)
Lung cancer No Yes (Heavy smokers)
Liver cancer No Yes (Hepatitis B carriers)
Prostate cancer No Yes (Strong family history)
NPC No Yes (Strong family history)

16. Mammography

17. Mammography

18. Screening Mammogram
Study Protocol Frequency Population Subgroup Invited Control F/U RR (95%CI)
HIP 2V MM, q12m x 4 40-64 40-49 14432 14701 18 0.77(0.53-1.11)
(1963-1969) CBE 50-64 16568 16299 18 0.80(0.59-1.08)
Edinburgh 1 or 2V q24m x4 45-64 45-49 11755 10641 14 0.83(0.54-1.27)
(1979-1988) MM, CBE 50-64 11245 12359 10 0.85(0.62-1.15)
Kopparberg 1V MM q24mx4 40-74 40-49 9650 5009 20 0.76(0.42-1.40)
(1977-1985) 50-74 28939 13551 20 0.52(0.39-0.70)
Ostergotland 1V MM q24mx4 40-74 40-49 10240 10411 20 1.06(0.65-1.76)
(1977-1985) 50-74 28229 26830 20 0.81(0.64-1.03)
Malmo 1 or 2V MM q18-24m x5 45-69 45-49 13528 12242 12.7 0.64(0.45-0.89)
(1976-1990) 50-69 17134 17165 9 0.86(0.64-1.16)
Stockholm 1V MM q28mx2 39-59 39-49 11724 12015 11.4 1.01(0.51-2.02)
(1981-1985) 50-59 9276 14217 7 0.65(0.4-1.08)
Gothenberg 2V MM q18mx5 39-59 39-49 11724 14217 12 0.56(0.32-0.98)
(1982-1988) 50-59 9276 16394 13 0.91(0.61-1.36)
CNBSS1 2V MM Q12m x5 40-49 40-49 25214 25216 11-16 1.07(0.75-1.52)
CNBSS2 CBE 50-59 50-59 19711 19694 13 1.02(0.78-1.33)
(1980-1987)
UK AGE 2V MM Q12m x 7 39-41 - 53914 107007 11 0.83 (0.66-1.04)
(1991-1997) year 1 then
1 V MM
Smith RA, Dorsi CJ. Screening for breast cancer in : Diseases of
the breast, Lippincott WW, Philadelphia USA, 2004

19. Benefits and Risks
Fletcher and Elmore, New Engl J Med 2003
Warner, New Engl J Med 2011

20. Impact at Population Level
Trends in female breast cancer mortality rates by ethnicity, USA 1975-2002

21. Screening Mammography Guidelines
Agency Frequency Age 40-49 Age 50-69 Age>69
US Preventive Services 2 yrs Discuss Yes Yes
Task Force Q2 yrs
Canadian Task Force on 1-2 yrs Discuss Yes No
Preventive Health Care
ACS 1 yr Yes Yes Yes
NCI 1-2 yrs Yes Yes Yes
HPB Singapore/MOH 2 years Discuss Yes -
Q1 year

22. Other Modalities
– MRI
• Prospective data in familial breast cancer1,2
• Higher sensitivity, lower specificity
• Impact on mortality not determined
• Higher cost
– Digital mammography
• Recent randomised trial showed higher accuracy in women
age <503
1. Warner E et al. JAMA 292:1317, 2004
2. Kriege M et al. NEJM 351:427, 2004
3. Pisano ED et al. NEJM 353:1846, 2005

23. Colon Cancer Screening

24. What is Colorectal Cancer

25. Symptoms and Signs of Colorectal
Cancer
• Blood in stools
• Change in stool calibre
• Change in bowel habits
• Sense of incomplete bowel emptying
• Abdominal distention
• Weight loss
• Anemia

26. Why is Screening Useful?
• There is a long period in the early stages
where there are no symptoms.
• Colorectal cancer develops from polyps or
adenomas. Removing polyps prevents
cancer.

27. How is Screening Performed?
• Faecal Tests
– Occult blood test
• Guaic based
• Immunohistochemical test
– Stool DNA
• Colonoscopy
• Virtual (CT) colonoscopy
• Flexible sigmoidoscopy
• Double contrast barium enema

28. Faecal Occult Blood Tests
• Detection of microscopic amounts of blood in the
stool
• Cancers may bleed an invisible amount during the
early stages
• Different types of test kits are available
– Guaic based
– Immunohistochemistry

29. Faecal Occult Blood Test

30. Faecal Occult Blood Test

31. Faecal Occult Blood Test
• If positive, colonoscopy required
• If negative, may be sampling error

32. Faecal Occult Blood Test
• False positive
– Diverticular disease
– Haemorrhoids
– Guaic based: red meat, raw turnips, broccoli,
cauliflower, radish
• False negative (guaic based tests)
– Non bleeding polyp/ tumour
– Medications: aspirin, NSAIDS, vitamin C >750 mg
per day

33. Benefits of FOBT
• Incidence of stage 4 reduced by 32-47%
• Incidence of colorectal cancer reduced by 20%
• Death from colorectal cancer reduced by
between 15% to 30%
– Absolute benefit 0.8-4.6 per 1000 patients
screened
– Numbers needed to screen 217-1250
Walsh et al. JAMA 2003

34. Colonoscopy
• Gold standard
• Enables screening and
intervention
• No randomized trials
• Based on cohort studies
– Reduces incidence of
colorectal cancer by 76%
– False negative rate 5-
12%
– Complication rate 0.03-
0.17%

35. Who, When, How Often

36. What is Cervical Cancer

37. Symptoms and Signs of Cervical Cancer
• Vaginal bleed
– Intermenstrual
– Postcoital
• Vaginal discharge
• Backpain

38. Screening for Cervical Cancer

39. Cervical Cancer
• Rationale for Screening
– No randomized trials
– Convincing evidence from observational
studies
• Introduction of screening programs
– Decreased incidence of cervical cancer
– Decreased cervical cancer deaths
– Calculations suggest 90% reduction in cervical
cancer mortality

40. Cervical Cancer Primary Prevention
• Bivalent
• Quadrivalent
• Best efficacy when given prior to HPV
exposure
• Does not alter need for screening

41. Ministry of Health Guidelines on Screening
• Cervix
– Women who have had sex before or are
sexually active should go for a Pap smear
once every 3 years
– Start at age 25

42. Conclusion
• Effective cancer screening is available for
common malignancies
• Cancer awareness and compliance with
screening recommendations can contribute to
healthy aging workforce
• Seek help from a medical professional to tailor
a suitable screening program
• Avoid overzealous screening