Why study changes in breast cancer rates over time? How did we study these changes in breast cancer rates?

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1 Breast Cancer Trends in Hong Kong: What are the Implications for Screening, Diagnosis and Management in All Chinese Women? GM Leung, TH Lam, TQ Thach, AJ Hedley Department of Community Medicine, HKU W Foo, Queen Elizabeth Hospital and Hong Kong Cancer Registry J Kong, Pamela Youde Nethersole Eastern Hospital R Fielding, WWT Lam Centre for Psycho-Oncological Research and Teaching, Department of Community Medicine, HKU January 16, 2003 Why study changes in breast cancer rates over time? To identify possible changes in population risk factors in Hong Kong To inform and predict future trends in Hong Kong and the rest of Asia How did we study these changes in breast cancer rates? Using data from the HK Cancer Registry Statistical techniques to separate out the influences of: - The ageing population - Changes in the external environment - Generation effects i.e. different risks for women born in different years (between 1900 and 1960) RISK Age-standardised incidence per 100, Are breast cancer rates increasing in Hong Kong? 37% increase over 27 years Year Average annual percentage change (%) Which age groups have had an increase? What accounted for the increase in breast cancer rates? Most of the changes were due to generation effects - i.e. women s increased risk of breast cancer was a result of their birth date For example, we observed a 2-fold difference between women born in 1900 and All ages Age (years) 1

2 RISK Relative risk (log scale) Increasing risk: the generation effect What factors are reflected in the generation effects relevant to HK? Late marriage, low fertility and late age of first pregnancy A more affluent lifestyle Low physical activity levels Increasing obesity Early puberty Central year of birth What are the implications of these findings for: Mass population screening by: Mammography? breast self examination? Diagnosis & management: medical treatment? psychological aspects? Cancer Screening: Where are we now in HK? In Shanghai, no survival benefit for regular breast self-examination No HK data on the effectiveness of mass screening by mammography All studies on screening mammography undertaken only in Western countries We therefore carried out an evidencebased review of the Western literature What do Western studies show? Risk ratio HIP 0.87 Malmo 0.81 Ostergotland 0.75 Kopparberg 0.58 Edinburgh 0.86 CNBSS II 1.02 Stockholm 0.74 Gothenburg 0.81 Overall 0.80 Can the test prevent death due to breast cancer in Western women? Western evidence shows a 20% benefit of delayed death from breast cancer (but not necessarily all causes) Benefit Harm Risk ratio 2

3 Breast cancer rates in different countries Is Hong Kong in a transition? China South Central Asia South Eastern Asia Western Asia Japan Hong Kong Western Europe Nothern Europe LOW HIGH Australia/ New Zealand North America Age-Standardised Incidence (per 100,000) in 1990 What are the implications of a relatively low breast cancer rate? Low accuracy of positive test results Of every 100 women who get a positive result from the screening test, at least 86 and as many as 98 will turn out to be Source: International Agency for Research on Cancer FALSE POSITIVES Why are false positives a problem for women? Positive screen results invariably lead to further confirmatory testing Such as fine needle aspiration or even open biopsy (surgery) Possible complications, including haematoma (bleeding) and wound infection, occur at a rate of 8%-10% Unnecessary anxiety and psychological burden for false positive women How many women do we need to screen to save one from dying of breast cancer? (Number Needed to Screen or NNS) If we screen all women aged 50 and over in HK annually for 10 years, assuming 100% uptake and follow-up, and assuming the 20% risk reduction seen in Western women: NNS for HK women = 1,302 US women = 666 3

4 Screened = 100,000 Natural History of Breast Cancer - the dilemma of ductal carcinoma in situ (DCIS) Positive = 10,370 False positive = 8,980 DCIS are early cancers confined to the milk ducts of the breast We currently do not know their clinical significance BUT if we find them, they are surgically removed (precautionary principle) Lives saved = 77 Complications = 134 Are DCIS common? US SEER programme (Cancer Registry) DCIS incidence 200% higher than expected in 1992 when mammography became widespread, based on trends in Ernster et al. JAMA. 1996;275:913-8 Kwong Wah Hospital mammography programme 53% of all abnormal screens were DCIS on trends in Lau et al. Aust NZ J Surg. 1998;68: What is the prognosis of DCIS? The absolute risk of breast cancer death among women with DCIS - 1.9% in 10 yrs Ernster et al. Arch Intern Med. 2000;160:953-8 Excellent survival of women with DCIS is probably NOT due to screening (but a combination of lead time and length bias) Miller AB et al. J Natl Cancer Inst. 2000;92: key differences between Chinese and Western women Ethnic differences in breast cancer risk, value of a positive screening test low in Chinese High number needed to screen to yield cancer-related mortality in Chinese Uncertain natural history of breast cancer - the DCIS dilemma We need to focus on the balance of benefit, harm and cost Conclusions (1) Currently insufficient evidence to justify population-based, mass screening by mammography in Chinese women However, women at high risk for the disease need careful individual clinical assessment e.g. - previous breast cancer - 2 first degree relatives - previous abnormal biopsy 4

5 Conclusions (2) Diagnostic vs Screening mammography breast imaging by mammography is a very useful tool for diagnosis of symptomatic patients but it is a poor instrument for screening asymptomatic Chinese women Conclusions (3) Resources that may be allocated for mass screening would be better directed at: Raising public awareness ( Be Breast Aware ) Promoting medical attention when symptoms appear Enhancing treatment services waiting time chemotherapy surgery radiotherapy psychological counselling Incidence of Top 10 Cancers in Female Age-Standaradized Rate Breast Lung Colon Rectum Cervix Stomach Liver Corpus Ovary NPC The only documented effective method of early detection of breast cancer is mammographic screening..;.but screening is not the only way to reduce mortality Year Investment: Mammographic units Trained radiologists Trained surgeons and pathologists Administrative system Education and Promotion Better investment: Trained surgeons and pathologists To strengthen definitive treatment To strengthen adjuvant treatment Conclusion: As demonstrated by the HKU report, alarming increase in incidence (but actually decreasing mortality) Conditions NOT RIPE to introduce mammographic screening - disproportionately high demand on resources, wasted efforts of screened women Need for a risk model to define high risk group more cost-effective in screening for the purpose of reducing mortality 5

6 Impacts of diagnosis and treatment on breast cancer patients High level of physiological and psychological distress ~ 1 patient in every 2 experiences anxiety and depression Delayed adjustment Increased family burden Increased use of medical services Local studies show psychosocial impact of breast cancer Diagnosis and treatment is a prolonged, multistage process that is very stressful Breast cancer diagnosis is profoundly shocking Women choose more extreme surgery to quicken return to normal life Psychosocial adjustment is better in women - who are more satisfied with participation in decisions about treatment -when treatment outcomes match expectations Implications More attention should be given to consultations in breast cancer Careful and continuing support is needed to help women make several treatment decisions After treatment rehabilitation can be developed to support women s return to their normal lives New development in Department of Community Medicine, HKU Mission: Identify key psychosocial and behavioural issues in the prevention and treatment of and adaptation to cancers in Chinese and other Asian people Offer evidence-based training to health workers caring for people with cancer Develop psychosocial clinical practice guidelines based on local research, emphasis on patientcentred care to address these issues 6