1640 dr wong nan soon cancer screening and saving lives, healthcare costs
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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
Avoid Overzealous Screening!
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
Scope
• Biology of cancer
• Cancer epidemiology in Singapore
• Principles behind screening
• Details of screening tests available
What Exactly is Cancer?
Hanahan and Weinberg. Cell 2011
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
Cancer: Top Killer in Singapore
Ministry of Health: Statistics
Cancer Burden
Singapore Cancer Registry Interim Report 2005-2009
Common Cancers by Gender
Singapore Cancer Registry Interim Report 2005-2009
Age Specific Cancer Incidence
Singapore Cancer Registry Interim Report 2005-2009
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
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
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
Evaluating Screening Test Avoiding Bias
• Screen detected cancers vs symptomatic cancers
– Lead time bias
– Length time bias
– Overdiagnosis bias
– Selection bias
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)
Mammography
Mammography
Screening Mammogram
Study Protocol Frequency Population Subgroup Invited Control F/U RR (95%CI)
HIP
(1963-1969)
2V MM,
CBE
q12m x 4 40-64 40-49
50-64
14432
16568
14701
16299
18
18
0.77(0.53-1.11)
0.80(0.59-1.08)
Edinburgh
(1979-1988)
1 or 2V
MM, CBE
q24m x4 45-64 45-49
50-64
11755
11245
10641
12359
14
10
0.83(0.54-1.27)
0.85(0.62-1.15)
Kopparberg
(1977-1985)
1V MM q24mx4 40-74 40-49
50-74
9650
28939
5009
13551
20
20
0.76(0.42-1.40)
0.52(0.39-0.70)
Ostergotland
(1977-1985)
1V MM q24mx4 40-74 40-49
50-74
10240
28229
10411
26830
20
20
1.06(0.65-1.76)
0.81(0.64-1.03)
Malmo
(1976-1990)
1 or 2V MM q18-24m x5 45-69 45-49
50-69
13528
17134
12242
17165
12.7
9
0.64(0.45-0.89)
0.86(0.64-1.16)
Stockholm
(1981-1985)
1V MM q28mx2 39-59 39-49
50-59
11724
9276
12015
14217
11.4
7
1.01(0.51-2.02)
0.65(0.4-1.08)
Gothenberg
(1982-1988)
2V MM q18mx5 39-59 39-49
50-59
11724
9276
14217
16394
12
13
0.56(0.32-0.98)
0.91(0.61-1.36)
CNBSS1
CNBSS2
(1980-1987)
2V MM
CBE
Q12m x5 40-49
50-59
40-49
50-59
25214
19711
25216
19694
11-16
13
1.07(0.75-1.52)
1.02(0.78-1.33)
UK AGE
(1991-1997)
2V MM
year 1 then
1 V MM
Q12m x 7 39-41 - 53914 107007 11 0.83 (0.66-1.04)
Smith RA, Dorsi CJ. Screening for breast cancer in : Diseases of the breast, Lippincott WW, Philadelphia USA, 2004
Benefits and Risks
Fletcher and Elmore, New Engl J Med 2003
Warner, New Engl J Med 2011
Impact at Population Level
Trends in female breast cancer mortality rates by ethnicity, USA 1975-2002
Screening Mammography Guidelines
Agency Frequency Age 40-49 Age 50-69 Age>69
US Preventive Services
Task Force
2 yrs Discuss
Q2 yrs
Yes Yes
Canadian Task Force on
Preventive Health Care
1-2 yrs Discuss Yes No
ACS 1 yr Yes Yes Yes
NCI 1-2 yrs Yes Yes Yes
HPB Singapore/MOH 2 years Discuss
Q1 year
Yes -
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
Colon Cancer Screening
What is Colorectal Cancer
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
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.
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
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
Faecal Occult Blood Test
Faecal Occult Blood Test
Faecal Occult Blood Test
• If positive, colonoscopy required
• If negative, may be sampling error
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
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
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%
Who, When, How Often
What is Cervical Cancer
Symptoms and Signs of Cervical Cancer
• Vaginal bleed
– Intermenstrual
– Postcoital
• Vaginal discharge
• Backpain
Screening for Cervical Cancer
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
Cervical Cancer Primary Prevention
• Bivalent
• Quadrivalent
• Best efficacy when given prior to HPV exposure
• Does not alter need for screening
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
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