Papers for this review were identified by searches of PubMed with the terms “breast cancer”, “mortality”, “population statistics”, and “decline”. References from between 1980 and 2002 were selected. Additional papers were identified from the reference lists of some articles. No language restrictions were applied.
Personal ViewWhy is breast-cancer mortality declining?
Section snippets
Reduction in risk
Mammography screening allows much earlier detection and diagnosis of breast cancer, but also detects some non-progressive cancers. Thus, the incidence of breast cancer artificially increased after the introduction of mammography screening programmes in the late 1980s. However, this increase in incidence was less than expected, which suggested that there was also a decline in the inherent risk of developing the disease.4 The recent decline in mortality might, therefore, be partly explained by a
Mammography screening
Eight randomised prospective trials have examined the effect of mammography screening on breast-cancer mortality.9 Overviews of these trials have shown that a relation between reduction in breast-cancer mortality and mammography screening takes 7–10 years to emerge. Patients with cancers that were detected before screening began were excluded from the studies. However, in population statistics, the cancers detected before the introduction of screening are not excluded from the total number of
The role of therapy
In the 1980s, there were substantial advances in the treatment of breast cancer. The results of several large randomised trials indicated that adjuvant systemic therapy could decrease breast-cancer mortality by about 20%.17 This benefit emerged about 3 years after these trials had begun. By the late 1980s, tamoxifen and polychemotherapy were widely prescribed in many developed countries as adjuvant therapy after surgery for primary breast cancer. Any favourable effect of adjuvant systemic
Earlier detection of palpable cancers
In the 1980s, there was a heightened awareness of breast cancer by both physicians and the public, and the number of patients with small, palpable tumours referred for treatment increased. We suggest that the earlier detection of palpable cancers has had a significant role in the decline in breast-cancer mortality.
Indeed, we could speculate that the entire benefit of breast-cancer screening is attributable to the earlier detection of palpable cancers, with detection of impalpable cancers
Conclusion
Olsen and Gøtzsche reported imbalances between control and study groups in several of the mammography screening trials and questioned the validity of their results.22 In their assessment, only the CNBSS trial was without bias. Thus, careful scrutiny of the age-adjusted breast-cancer mortality statistics is extremely relevant in elucidating the potential effect of mammography screening. Age-adjusted mortality rates are the most basic measure of progress against cancer. If novel strategies in the
Search strategy and selection criteria
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Breast cancer screening
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How much of the recent rise in breast cancer incidence can be explained by increase in mammography utilization?
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Birth cohort and calender period trends in breast cancer mortality in the United States and Canada
J Natl Cancer Inst
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Re: recent trends in US breast cancer incidence, survival, and mortality rates
J Natl Cancer Inst
(1997) - et al.
Breastfeeding and breast cancer risk to age 50 among women in Germany
Cancer Causes Control
(2000)
Breast cancer and breastfeeding: collaborative reanalysis of individual data from 47 epidemiological studies in 30 countries, including 50 302 women with breast cancer and 96 973 women without the disease
Lancet
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