Elsevier

The Lancet Oncology

Volume 2, Issue 3, March 2001, Pages 133-140
The Lancet Oncology

Review
Epidemiology of breast cancer

https://doi.org/10.1016/S1470-2045(00)00254-0Get rights and content

Summary

Breast cancer is the commonest cause of cancer death in women worldwide. Rates vary about five-fold around the world, but they are increasing in regions that until recently had low rates of the disease. Many of the established risk factors are linked to oestrogens. Risk is increased by early menarche, late menopause, and obesity in postmenopausal women, and prospective studies have shown that high concentrations of endogenous oestradiol are associated with an increase in risk. Childbearing reduces risk, with greater protection for early first birth and a larger number of births; breastfeeding probably has a protective effect. Both oral contraceptives and hormonal therapy for menopause cause a small increase in breast-cancer risk, which appears to diminish once use stops. Alcohol increases risk, whereas physical activity is probably protective. Mutations in certain genes greatly increase breastcancer risk, but these account for a minority of cases.

Section snippets

Age

The incidence of breast cancer increases rapidly with age during the reproductive years and then increases at a slower rate after about age 50 years, the average age at menopause (Figure 2). The cumulative incidence of breast cancer among women in Europe and North America is about 2.7% by age 55, about 5.0% by age 65, and about 7.7% by age 75.2

International variation, effects of migration, and time trends

Both incidence of and mortality from breast cancer vary about five-fold among populations around the world (Figure 3). Rates are high in most of the more developed countries but low in less developed countries and in Japan (though rates in Japan are rising). Among migrants from low-risk to high-risk countries, the rates increase and eventually become similar to those among the rest of the population in the new country. A study of migrants from eastern Asia to the USA showed that the increase in

Menarche and the menstrual cycle

The older a woman is when she begins menstruating, the lower her risk of breast cancer.7 For each 1-year delay in menarche, the risk decreases by around 5%.8 There is also evidence that, although age at menarche is related to breastcancer risk at all ages, the effect may be stronger in younger (premenopausal) women.7 Other menstrual factors, such as cycle length and regularity, have not been consistently related to risk of breast cancer.

Childbearing

Childbearing seems to have a dual effect on risk of breast

Lifestyle

The classic risk factors for breast cancer, such as age at menarche, age at menopause, and parity, are not amenable to change for the purpose of reducing risk. However, other behavioural risk factors could be modified, and these changes to reduce the risk of breast cancer would have other health benefits: avoidance of obesity should reduce the risk of other diseases also; limitation of alcohol intake would be beneficial; breastfeeding is also beneficial for the baby; and maintenance of at least

Search strategy and selection criteria

Papers cited were identified through MEDLINE and references from relevant articles, selected on the basis of the largest-scale and highest-quality evidence for each topic discussed, and on the basis of the authors' interpretation of the overall evidence available. Only papers published in English were included.

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