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Reproductive factors and risk of premenopausal breast cancer by age at diagnosis: are there differences before and after age 40?

Abstract

We examined the relationship between reproductive factors and risk of premenopausal breast cancer among women less than age 40 compared with older premenopausal women. We documented 374 incident cases of breast cancer diagnosed before age 40, and 2,533 cases diagnosed at age 40 and older among premenopausal women in the Nurses' Health Study cohorts. Biennial questionnaires were used to determine age at menarche, age at first birth, parity, breastfeeding, and other reproductive factors. Multivariate relative risks (RR) and 95 % confidence intervals (CI) were calculated using Cox proportional hazards models within age at diagnosis groups. Tumors in younger women were significantly more likely to be higher grade, larger size, and hormone receptor negative than were tumors in older premenopausal women (p < 0.0001). There was no significant heterogeneity according to age in associations between reproductive factors and risk of premenopausal breast cancer. First birth at age 30 or older increased breast cancer risk in both age groups (age <40: RR 1.10, 95 % CI 0.80-1.50; age ≥ 40: RR 1.16, 95 % CI 1.02-1.32; p-heterogeneity = 0.44). Risk of premenopausal breast cancer decreased with each additional year of age at menarche in both age groups (age <40: RR 0.93, 95 % CI 0.87-0.99; p trend = 0.02; age ≥ 40: RR 0.94, 95 % CI 0.91-0.97; p trend = <0.0001). Among premenopausal parous women, breastfeeding was protective regardless of age at diagnosis (age <40: RR 0.84, 95 % CI 0.57-1.22; age ≥ 40: RR 0.85, 95 % CI 0.72-0.99; p-heterogeneity = 0.79). In the largest prospective examination of reproductive risk factors and risk of breast cancer before and after age 40, we found that younger women were more likely to develop tumors with less favorable prognostic characteristics. However, associations between reproductive factors and risk of breast cancer were similar regardless of age at diagnosis of premenopausal breast cancer.

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  • Authors+Show Affiliations

    ,

    Department of Epidemiology, Harvard School of Public Health, Boston, MA, USA, ewarner@hsph.harvard.edu.

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    Source

    Breast cancer research and treatment 142:1 2013 Nov pg 165-75

    MeSH

    Adult
    Age Factors
    Age of Onset
    Breast Neoplasms
    Contraceptives, Oral
    Female
    Humans
    Incidence
    Menarche
    Middle Aged
    Parity
    Pregnancy
    Premenopause
    Reproductive History
    Risk
    Young Adult

    Pub Type(s)

    Journal Article
    Research Support, N.I.H., Extramural
    Research Support, U.S. Gov't, Non-P.H.S.

    Language

    eng

    PubMed ID

    24136668

    Citation

    Warner, Erica T., et al. "Reproductive Factors and Risk of Premenopausal Breast Cancer By Age at Diagnosis: Are There Differences Before and After Age 40?" Breast Cancer Research and Treatment, vol. 142, no. 1, 2013, pp. 165-75.
    Warner ET, Colditz GA, Palmer JR, et al. Reproductive factors and risk of premenopausal breast cancer by age at diagnosis: are there differences before and after age 40? Breast Cancer Res Treat. 2013;142(1):165-75.
    Warner, E. T., Colditz, G. A., Palmer, J. R., Partridge, A. H., Rosner, B. A., & Tamimi, R. M. (2013). Reproductive factors and risk of premenopausal breast cancer by age at diagnosis: are there differences before and after age 40? Breast Cancer Research and Treatment, 142(1), pp. 165-75. doi:10.1007/s10549-013-2721-9.
    Warner ET, et al. Reproductive Factors and Risk of Premenopausal Breast Cancer By Age at Diagnosis: Are There Differences Before and After Age 40. Breast Cancer Res Treat. 2013;142(1):165-75. PubMed PMID: 24136668.
    * Article titles in AMA citation format should be in sentence-case
    TY - JOUR T1 - Reproductive factors and risk of premenopausal breast cancer by age at diagnosis: are there differences before and after age 40? AU - Warner,Erica T, AU - Colditz,Graham A, AU - Palmer,Julie R, AU - Partridge,Ann H, AU - Rosner,Bernard A, AU - Tamimi,Rulla M, Y1 - 2013/10/18/ PY - 2013/09/10/received PY - 2013/09/30/accepted PY - 2013/10/19/entrez PY - 2013/10/19/pubmed PY - 2014/6/10/medline SP - 165 EP - 75 JF - Breast cancer research and treatment JO - Breast Cancer Res. Treat. VL - 142 IS - 1 N2 - We examined the relationship between reproductive factors and risk of premenopausal breast cancer among women less than age 40 compared with older premenopausal women. We documented 374 incident cases of breast cancer diagnosed before age 40, and 2,533 cases diagnosed at age 40 and older among premenopausal women in the Nurses' Health Study cohorts. Biennial questionnaires were used to determine age at menarche, age at first birth, parity, breastfeeding, and other reproductive factors. Multivariate relative risks (RR) and 95 % confidence intervals (CI) were calculated using Cox proportional hazards models within age at diagnosis groups. Tumors in younger women were significantly more likely to be higher grade, larger size, and hormone receptor negative than were tumors in older premenopausal women (p < 0.0001). There was no significant heterogeneity according to age in associations between reproductive factors and risk of premenopausal breast cancer. First birth at age 30 or older increased breast cancer risk in both age groups (age <40: RR 1.10, 95 % CI 0.80-1.50; age ≥ 40: RR 1.16, 95 % CI 1.02-1.32; p-heterogeneity = 0.44). Risk of premenopausal breast cancer decreased with each additional year of age at menarche in both age groups (age <40: RR 0.93, 95 % CI 0.87-0.99; p trend = 0.02; age ≥ 40: RR 0.94, 95 % CI 0.91-0.97; p trend = <0.0001). Among premenopausal parous women, breastfeeding was protective regardless of age at diagnosis (age <40: RR 0.84, 95 % CI 0.57-1.22; age ≥ 40: RR 0.85, 95 % CI 0.72-0.99; p-heterogeneity = 0.79). In the largest prospective examination of reproductive risk factors and risk of breast cancer before and after age 40, we found that younger women were more likely to develop tumors with less favorable prognostic characteristics. However, associations between reproductive factors and risk of breast cancer were similar regardless of age at diagnosis of premenopausal breast cancer. SN - 1573-7217 UR - https://www.unboundmedicine.com/medline/citation/24136668/Reproductive_factors_and_risk_of_premenopausal_breast_cancer_by_age_at_diagnosis:_are_there_differences_before_and_after_age_40 L2 - https://doi.org/10.1007/s10549-013-2721-9 DB - PRIME DP - Unbound Medicine ER -