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Breast cancer risk and hormone receptor status in older women by parity, age of first birth, and breastfeeding: a case-control study.

Lord, Sarah J and Bernstein, Leslie and Johnson, Karen A and Malone, Kathleen E and McDonald, Jill A and Marchbanks, Polly A and Simon, Michael S and Strom, Brian L and Press, Michael F and Folger, Suzanne G and Burkman, Ronald T and Deapen, Dennis and Spirtas, Robert and Ursin, Giske (2008) Breast cancer risk and hormone receptor status in older women by parity, age of first birth, and breastfeeding: a case-control study. Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology, 17 (7). pp. 1723-1730. ISSN 1055-9965

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BACKGROUND: Early age at first birth and multiparity reduce the risk of estrogen receptor-progesterone receptor (ERPR)-positive breast cancer, whereas breastfeeding reduces the risk of both ERPR-positive and ERPR-negative cancers. METHODS: We used multivariable logistic regression analysis to investigate whether age at first birth (<25 or > or =25 years) and breastfeeding (ever/never) modify the long-term effect of parity on risk of ERPR-positive and ERPR-negative cancer using 1,457 incident breast cancer cases and 1,455 controls ages > or =55 years who participated in the Women's Contraceptive and Reproductive Experiences Study. RESULTS: Women who gave birth before age 25 years had a 36% reduced risk of breast cancer compared with nulligravida that was not observed for women who started their families at an older age (P(heterogeneity) = 0.0007). This protective effect was restricted to ERPR-positive breast cancer (P(heterogeneity) = 0.004). Late age at first birth increased the risk of ERPR-negative cancers. Additional births reduced the risk of ERPR-positive cancers among women with an early first birth (P(trend) = 0.0001) and among women who breastfed (P(trend) = 0.004) but not among older mothers or those who never breastfed. In women with a late first birth who never breastfed, multiparity was associated with increased risk of breast cancer. CONCLUSIONS: These findings suggest that the effect of parity on a woman's long-term risk of breast cancer is modified by age at first full-term pregnancy and possibly by breastfeeding.

Item Type: Article or Abstract
Additional Information: This article is freely available via the URL above.
DOI: 10.1158/1055-9965.EPI-07-2824
PubMed ID: 18628424
PMCID: PMC2754711
Grant Numbers: R01 CA098858, N01 PC067006, N01 CN065064
Keywords or MeSH Headings: Adult; Age Factors; Breast Feeding/epidemiology; Breast Neoplasms/blood/epidemiology; Female; Follow-Up Studies; Humans; Middle Aged; Morbidity; Parity; Pregnancy; Prognosis; Receptors, Estrogen/blood; Receptors, Progesterone/blood; Retrospective Studies; Risk Factors; Time Factors; Tumor Markers, Biological/blood; United States/epidemiology; Young Adult;
Subjects: Diseases > Solid tumors > Breast cancer
Research Methodologies > Epidemiology > Risk assessment
Cellular and Organismal Processes > Reproduction
Depositing User: Library Staff
Date Deposited: 31 Jul 2009 20:26
Last Modified: 14 Feb 2012 14:42

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