Download Screen Mammography: Regret or no regret?

Screening Mammography:
Regret or no regret?
Joint Hospital Surgical Grand Round
19 May 2007
Yvonne Tsang
Prince of Wales Hospital
Screening – WHO criteria
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Routine examination of asymptomatic population for a
disease
Criteria
1.
2.
3.
4.
5.
6.
7.
8.
9.
Important health problem
Accepted treatment available
Facilities for diagnosis and treatment are available
Condition can be recognizable in latent/early stage
Suitable tests for screening available
The screening test is acceptable to population
Natural history of disease is well understood
Agreed policy on whom to treat is available
The cost of diagnosis and treatment should be economically
balanced
10. Case finding should be continued
Wilson JHG. The Principle and Practice of Screening for disease.
Public Health Paper. Geneva 1968
Breast cancer
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Suitable for screening
Pre-malignant stage
Early detection would affect management
Acceptance is high in Western countries
Screening mammography is widely
recommended in Western countries for
women age 50 years or older
Breast cancer
• Highest incidence among all female
cancers in Hong Kong since 1994
• Incidence is rising
• 22% of all cancers in women in 2004
• Cumulative life-time risk is 1 in 22
» Hospital Authority Hong Kong Cancer Registry
Incidence and mortality
Hong Kong Cancer Registry 2004
New Case
Death
2,273
454
Rank
1
3
Relative Frequency (%)
22
9.9
Median age (years)
52
60
63.7
12.7
1 in 22
1 in 106
Number of cases registered
Crude Rate
Cumulative life-time risk (0-74 yrs)
Mortality : Incidence Ratio
0.20
Hong Kong Cancer Registry
Mammogram
• Two views of each breast
– CC and MLO views
Suspicious lesions
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Mass
clustered microcalcifications
architectural distortion
asymmetry
Performance
Specificity
Sensitivity
PPV
89.2
83.1
4.1
40-44
87.2
72.2
1.3
45-49
87.6
80.3
2.2
50-54
88.6
82.3
3.1
55-59
89.4
83.9
4.5
60-64
90.0
84.6
5.3
65-69
90.6
86.6
6.5
70-74
91.6
84.6
7.9
>= 75
92.0
84.5
8.9
All mammograms
Age at mammography
Joshua J. Fenton et al. NEJM Apr 2007
Screening mammography - RCTs
Study
Start
day
Screening
interval
(months)
No. of
views
No. randomized
Screening control
New York
1963
12
2
30,131
30,565
Malmo
1976
21
2
21,088
21,195
Kopparberg
1977
24
1
38,589
18,582
Ostergotland
1977
24
1
38,491
37,403
Edinburgh
1979
24
2 then 1 22,926
21,342
Canadian
1980
12
2
44,925
44,910
Stockholm
1981
24 – 28
1
40,318
19,943
Gotenburg
1982
18
2
11,724
14,217
248,192
208,157
All studies
The health Insurance Plan (HIP) of
Greater New York trial
• The first RCT for screening
mammography
• > 60,000 women recruited
• Clinically significant reduction of
mortality for 30% in study group by 10
years
Results from RCTs
• Reduction in mortality was consistently
demonstrated for women age 50 years and
older
• Mortality reduction ~ 17 to 31%
– Swedish Two-Country Trial in 1977
– Edinburgh Trial 1979-1981
– Canadian National Breast Screening Study 1980-1985
Screening mammography - Meta-analysis
• Reduces breast cancer mortality in women
aged 50–74 after 7–9 years follow up
• Regardless of screening interval and no.
of views per screen
Kerliokowske K. et al. JAMA 1995
Jan11;273(2):149-54
Criticisms on previous RCTs
• Baseline imbalance in 6 of 8 RCTs
identified trials
• Inconsistencies in no. of women
randomized in 4 RCTs
• No effect of screening on improving
breast cancer mortality in the 2 adequately
randomized trials
Peter C Gotzsche, Ole Olsen. The Lancet. Jan 8,2000
Against screening mammography
• False positive
– 23% women screened had at least one false
positive mammogram over 10 years
– 49.1% cumulative risk of a false positive
results after 10 mammograms
– Unnecessary scanning, biopsies
– Anxiety, fear, worry
False positive
– For every $100 spent for screening, an
additional $33 was spent to evaluate false
positive results
» Ten-year risk of false positive screening
mammograms and clinical breast examinations.
NEJM Apr1998 338:1089-96
Digital vs Film mammography
• Accuracy of digital mammography is
higher especially in
– Women under age of 50
– Dense breasts
– Premenopausal or perimenopausal women
» Etta D. Pisano et al. NEJM Oct2005
NHS Breast cancer screening programme
• Since 1998
• 1.3 million women being screened each
year
• About 1 in 8 women screened regularly by
the NHSBCP will be recalled for
assessment at least once over 10 years
• Cancers in screened women are smaller
and less likely need mastectomy
NHS Breast cancer screening programme
• One fewer women will die from breast cancer
for every 400 women screened regularly by the
NHSBCP over 10-year period
• Currently NHSBCP saves ~1400 lives each year
in UK
• Spends about £3000 for every year of life saved
» NHSBSP Publication no 61 Feb 2006
Situation in Hong Kong
• No population screening for breast cancer
• Lower incidence compared with Western
countries
• The value of mammography screening
may be lower than Western countries
• No RCT
Estimated age-specific rates of breast cancer
incidence for women age 50 to 69 years
Muir C et al eds (1987) Cancer Incidence in Five Continents
International Agency for Research on Cancer and the International Association of Cancer
Registries, World Health Organisation, Lyon.
Situation in Hong Kong
• Number needed to screen in HK is 1302
women for 10 years compared with 666 in
US in year 1996
• Accuracy of mammogram is lower in
Chinese
– Average Chinese breast has a smaller volume
(224.5 cm3 vs 585.1 cm3 in British women)
– Denser with less fat content
Local data from KWH
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Opportunistic screening
5 – year period
31378 asymptomatic women
46637 mammograms performed
2 views, double reading
Crude cancer detection rate 5 per 1000
» Lui CY et al. Hong Kong Med J Apr 2007
Future
• Increasing breast
cancer awareness
• Opportunistic
screening services
Conclusions
• Increasing breast cancer incidence in HK
• Heightened public health awareness
• Ever-increasing demand for quality breast
screening
• Not only detect cancer
• Detecting early cancers leading to better
prognosis
• Feasibility of treatment with less morbidity
• Population screening?
The End
Thank you!