Journal of the National Cancer Institute Advance Access originally published online on September 9, 2008
JNCI Journal of the National Cancer Institute 2008 100(18):1270-1271; doi:10.1093/jnci/djn303
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© The Author 2008. Published by Oxford University Press.
EDITORIALS |
Screening for Breast Cancer in India—Is It An Appropriate Strategy?
Affiliation of author: Cancer Screening Evaluation Unit, Institute of Cancer Research, Sutton, Surrey, UK
Correspondence to: Sue Moss, PhD, Cancer Screening Evaluation Unit, Institute of Cancer Research, Sir Richard Doll Building, Cotswold Road, Sutton, Surrey SM2 5NG, UK (e-mail: sue.moss{at}icr.ac.uk).
Breast cancer is an increasing health problem in India (1). The trend of rising incidence rates is likely to continue due to further changes in lifestyle factors such as childbearing and dietary habits. The current age-standardized rate is 19.1 per 100 000 per annum, but, in contrast to what is observed in developed countries, the incidence rate peaks below age 50. Stage distribution at presentation is less favorable than in developed countries, with 50%–70% of cases presenting for treatment being locally advanced (2), and the availability and level of facilities for treatment are variable (3). Survival rates are consequently low (4), and there is a clear need to improve the availability and accessibility of facilities for diagnosis and treatment, as well as education and awareness (5).
Screening for breast cancer by mammography has been demonstrated by randomized controlled trials to be effective in reducing mortality from the disease, at least in women aged 50 and above, and organized population-based screening programs are now widely implemented in the developed world. Nevertheless, debate about the value of screening continues, in particular for women below age 50, for whom evidence for the balance of benefits and harms of screening is less clear. By contrast, screening by clinical breast examination (CBE) alone has not been demonstrated by randomized controlled trials to reduce mortality. An IARC Working Group concluded in 2002 that there is inadequate evidence that breast screening by CBE, either alone or together with mammography, can reduce mortality from breast cancer (6). However, cancers detected by CBE tend to be diagnosed at an earlier stage than those not detected by screening, suggesting a greater potential for effectiveness in a setting where stage at diagnosis is generally poor (7).
It therefore seems logical to consider the use of CBE as a screening modality in a country such as India, where limited resources may preclude the possibility of mammographic screening. In this issue of the Journal, Lamberts Okonkwo et al. (8) apply a microsimulation model of breast cancer screening to an Indian setting to predict the effect and cost-effectiveness of a range of screening policies including screening by CBE. Using this model, the authors predicted that biennial screening by CBE between the ages of 40 and 60 in India was at least as cost-effective as screening by mammography in developed countries although less cost-effective than cervical screening in developing countries, with a cost-effectiveness ratio of Int$1341 per life-year gained, compared with Int$3468 for mammography. Targeting women aged 40–60 was predicted to achieve a greater mortality reduction compared with targeting women aged 50–70.
All models such as this involve a number of assumptions regarding the natural history of the disease and the effect of the intervention; the current model necessitates assumptions about the stage shift achieved by CBE and the resulting impact on breast cancer mortality. The 16% estimated "steady-state" mortality reduction from biennial CBE results in the favorable cost-effectiveness ratio. Whether such a reduction would be achieved in actual practice is not clear. The model also predicts a 26% relative mortality reduction from biennial mammography between ages 40 and 60, a result similar in magnitude to the estimated effect of screening in developed countries (6). In the absence of detailed data from India, the authors have based estimates of the stage-specific survival from breast cancer on results from European studies. It is possible that in a setting with more limited treatment facilities, comparable survival rates would not be attained. In addition, although CBE may be a specific screening test, the trade-off between sensitivity and specificity means that sensitivity may be low (9), and there is a lack of trial data demonstrating effectiveness against which to benchmark performance.
Potential barriers to effective screening also include lack of necessary infrastructure and sociocultural influences on compliance. For screening to succeed, a high level of compliance is necessary, not only with initial screening but also with referral for further investigation in those screened positive, and with treatment in those with confirmed diagnosis. In a trial being conducted in Mumbai, compliance to diagnostic investigations among screen-positive women has been reported as 73% (10). A trial of CBE in the Philippines was discontinued due to poor adherence to follow-up in the first round (11).
It is important not to lose sight of the responsibilities associated with screening an asymptomatic and healthy population. The need for informed consent and informed choice to participate in screening and to explain both the potential harms and benefits of screening is now widely recognized. This may prove challenging in a developing country with relatively low levels of education and literacy, a problem compounded by the fact that there is no direct evidence on the benefit of screening by CBE.
Screening for breast cancer by any modality will result in false positives that will require further investigation with possible surgery to confirm the diagnosis; these incur not only financial costs also increased anxiety. The latter has been shown to be mostly short-lived in a Western setting, but that may differ in different cultures. There is also a potential for overdiagnosis of disease that would not otherwise present within a woman's lifetime. Although overdiagnosis may be less likely with CBE than mammography, lower life expectancy will increase the possibility that it will occur.
The success of population-based screening programs is likely to be related to the organization, infrastructure, and quality assurance involved. In addition, facilities for ongoing monitoring, including registers of cancer diagnoses and deaths, are essential if the performance of a program is to be evaluated and potential problems identified and corrected. The costs of a screening program need to be considered against other health interventions, such as those to reduce maternal mortality in a country where this account for over 100 000 deaths a year.
However, it is accepted that one of the benefits of organized screening in the United Kingdom (and probably other developed countries) has been to improve the standards of care and treatment for all women diagnosed with breast cancer, whether symptomatically or by screening, and also that the increased publicity and consequent awareness is likely to have led to a shift toward earlier symptomatic presentation (12). Such an effect might be one benefit of the introduction of screens in developing countries, but whether screening is the best means of achieving these important aims needs further exploration.
REFERENCES
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6. IARC Working Group on the Evaluation of Cancer-Preventive Strategies. IARC Handbooks of Cancer Prevention: Breast Cancer Screening (2002) Lyon, France: IARC Scientific Publications.
7. Duffy SW, Tabar L, Vitak B, Warwick J. Tumor size and breast cancer detection: what might be the effect of a less sensitive screening tool than mammography? Breast J (2006) 12(suppl_1):S91–S95.[CrossRef][Web of Science][Medline]
8. Lamberts Okonkwo Q, Draisma G, der Kinderen A, Brown ML, de Koning HJ. Breast cancer screening policies in developing countries: a cost-effectiveness analysis for India. J Natl Cancer Inst (2008) 100(18):1290–1300.
9. Fenton JJ, Barton MB, Geiger AM, et al. Screening clinical breast examination: how often does it miss lethal breast cancer? J Natl Cancer Inst Monogr (2005(35)) 67–71.
10. Dinshaw K, Mishra G, Shastri S, et al. Determinants of Compliance in a cluster randomised controlled trial on screening of breast and cervix cancer in Mumbai, India. Oncology (2007(3–4)) 73:154–161.[CrossRef]
11. Pisani P, Parkin DM, Ngelangel C, et al. Outcome of screening by clinical examination of the breast in a trial in the Philippines. Int J Cancer (2006) 118(1):149–154.[CrossRef][Web of Science][Medline]
12. Gray JA, Patnick J, Blanks RG. Maximising benefit and minimising harm of screening. BMJ (2008) 336(7642):480–483.
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