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BioMed Central, BMC Cancer, 1(13), 2013

DOI: 10.1186/1471-2407-13-584

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Reproductive factors and risk of hormone receptor positive and negative breast cancer: a cohort study

Journal article published in 2013 by Rebecca Ritte, Kaja Tikk, Annekatrin Lukanova, Anne Tjønneland, Anja Olsen ORCID, Kim Overvad ORCID, Laure Dossus, Agnès Fournier ORCID, Françoise Clavel-Chapelon, Verena Grote, Heiner Boeing, Krasimira Aleksandrova, Antonia Trichopoulou, Pagona Lagiou, Dimitrios Trichopoulos and other authors.
This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Abstract

Abstract Background The association of reproductive factors with hormone receptor (HR)-negative breast tumors remains uncertain. Methods Within the EPIC cohort, Cox proportional hazards models were used to describe the relationships of reproductive factors (menarcheal age, time between menarche and first pregnancy, parity, number of children, age at first and last pregnancies, time since last full-term childbirth, breastfeeding, age at menopause, ever having an abortion and use of oral contraceptives [OC]) with risk of ER-PR- (n = 998) and ER+PR+ (n = 3,567) breast tumors. Results A later first full-term childbirth was associated with increased risk of ER+PR+ tumors but not with risk of ER-PR- tumors (≥35 vs. ≤19 years HR: 1.47 [95% CI 1.15-1.88] p trend