Screening Mammography:
Regret or no regret?
Joint Hospital Surgical Grand Round
19 May 2007Yvonne Tsang
Prince of Wales Hospital
Screening – WHO criteria• Routine examination of asymptomatic
population for a disease• Criteria
1. Important health problem2. Accepted treatment available3. Facilities for diagnosis and treatment are available4. Condition can be recognizable in latent/early stage5. Suitable tests for screening available6. The screening test is acceptable to population7. Natural history of disease is well understood8. Agreed policy on whom to treat is available9. The cost of diagnosis and treatment should be
economically balanced10.Case finding should be continued
Wilson JHG. The Principle and Practice of Screening for disease. Public Health Paper. Geneva 1968
Breast cancer• 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 DeathNumber of cases registered
2,273 454
Rank 1 3Relative Frequency (%) 22 9.9Median age (years) 52 60Crude Rate 63.7 12.7Cumulative life-time risk (0-74 yrs)
1 in 22 1 in 106
Mortality : Incidence Ratio 0.20
Hong Kong Cancer Registry
Mammogram• Two views of each breast
– CC and MLO views
Suspicious lesions• Mass• clustered microcalcifications• architectural distortion• asymmetry
Performance
Joshua J. Fenton et al. NEJM Apr 2007
Specificity
Sensitivity
PPV
All mammograms 89.2 83.1 4.1Age at
mammography40-44 87.2 72.2 1.345-49 87.6 80.3 2.250-54 88.6 82.3 3.155-59 89.4 83.9 4.560-64 90.0 84.6 5.365-69 90.6 86.6 6.570-74 91.6 84.6 7.9>= 75 92.0 84.5 8.9
Screening mammography - RCTsStudy
Start
day
Screening
interval (months
)
No. of
views
No. randomized
Screening control
New York 1963 12 2 30,131 30,565Malmo 1976 21 2 21,088 21,195Kopparberg
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 44,910Stockholm 1981 24 – 28 1 40,318 19,943Gotenburg 1982 18 2 11,724 14,217All studies 248,19
2208,157
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 ContinentsInternational Agency for Research on Cancer and the International Association of Cancer R
egistries, 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• 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!
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