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The international variation in breast cancer rates: an epidemiological assessment.
Breast Cancer Res Treat 1991; 18 Suppl 1:S11-7BC

Abstract

Part of the international differences in breast cancer incidence rates can be explained by geographic variation in reproductive and other breast cancer risk factors. Age at menarche and age at onset of regular ovulatory menstrual cycles are two such factors; both vary across populations directly according to breast cancer risk, and both are acknowledged as breast cancer risk factors. Consideration of the body of evidence on these factors, as well as that on age at menopause, suggests that the cumulative frequency of ovulatory menstrual cycles is a critical determinant of breast cancer risk. Although age at first term pregnancy explains the majority of the protective effect of parity on breast cancer risk, two recent studies have demonstrated a small residual protective effect of increasing number of births. It appears that pregnancy has paradoxical effects on breast cancer risk in terms of hormone production and metabolism. The initial effect is an increased risk associated with first trimester estrogen exposure. However, the hormonal consequences of completing the pregnancy counteract this negative effect of early pregnancy. The effect of body weight, a breast cancer risk factor for postmenopausal women, can be explained in terms of increased extraglandular conversion of androstenedione to estrone. Further evidence supporting a pathogenic role of estrogens in the development of breast cancer comes from international studies of endogenous hormones in populations with differing risks of breast cancer. These risk factors have been incorporated into a mathematical model which is based on the concept that breast tissue ages according to hormonal (primarily estrogen) exposure; this model closely predicts the incidence rates throughout the world.

Authors+Show Affiliations

Department of Preventive Medicine, University of Southern California School of Medicine, Norris Cancer Hospital and Research Institute, Los Angeles 90033.No affiliation info available

Pub Type(s)

Journal Article
Review

Language

eng

PubMed ID

1873546

Citation

Henderson, B E., and L Bernstein. "The International Variation in Breast Cancer Rates: an Epidemiological Assessment." Breast Cancer Research and Treatment, vol. 18 Suppl 1, 1991, pp. S11-7.
Henderson BE, Bernstein L. The international variation in breast cancer rates: an epidemiological assessment. Breast Cancer Res Treat. 1991;18 Suppl 1:S11-7.
Henderson, B. E., & Bernstein, L. (1991). The international variation in breast cancer rates: an epidemiological assessment. Breast Cancer Research and Treatment, 18 Suppl 1, pp. S11-7.
Henderson BE, Bernstein L. The International Variation in Breast Cancer Rates: an Epidemiological Assessment. Breast Cancer Res Treat. 1991;18 Suppl 1:S11-7. PubMed PMID: 1873546.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - The international variation in breast cancer rates: an epidemiological assessment. AU - Henderson,B E, AU - Bernstein,L, PY - 1991/5/1/pubmed PY - 1991/5/1/medline PY - 1991/5/1/entrez SP - S11 EP - 7 JF - Breast cancer research and treatment JO - Breast Cancer Res. Treat. VL - 18 Suppl 1 N2 - Part of the international differences in breast cancer incidence rates can be explained by geographic variation in reproductive and other breast cancer risk factors. Age at menarche and age at onset of regular ovulatory menstrual cycles are two such factors; both vary across populations directly according to breast cancer risk, and both are acknowledged as breast cancer risk factors. Consideration of the body of evidence on these factors, as well as that on age at menopause, suggests that the cumulative frequency of ovulatory menstrual cycles is a critical determinant of breast cancer risk. Although age at first term pregnancy explains the majority of the protective effect of parity on breast cancer risk, two recent studies have demonstrated a small residual protective effect of increasing number of births. It appears that pregnancy has paradoxical effects on breast cancer risk in terms of hormone production and metabolism. The initial effect is an increased risk associated with first trimester estrogen exposure. However, the hormonal consequences of completing the pregnancy counteract this negative effect of early pregnancy. The effect of body weight, a breast cancer risk factor for postmenopausal women, can be explained in terms of increased extraglandular conversion of androstenedione to estrone. Further evidence supporting a pathogenic role of estrogens in the development of breast cancer comes from international studies of endogenous hormones in populations with differing risks of breast cancer. These risk factors have been incorporated into a mathematical model which is based on the concept that breast tissue ages according to hormonal (primarily estrogen) exposure; this model closely predicts the incidence rates throughout the world. SN - 0167-6806 UR - https://www.unboundmedicine.com/medline/citation/1873546/full_citation L2 - http://www.diseaseinfosearch.org/result/960 DB - PRIME DP - Unbound Medicine ER -