title: Age at first birth and the risk of breast cancer in BRCA1 and BRCA2 mutation carriers.
abstract: An early age at first full-term birth is associated with a reduction in the subsequent development of breast cancer among women in the general population. A similar effect has not yet been reported among women who carry an inherited BRCA1 or BRCA2 mutation. We conducted a matched case-control study on 1816 pairs of women with a BRCA1 (n = 1405) or BRCA2 (n = 411) mutation in an attempt to elucidate the relationship between age at first full-term pregnancy and the risk of developing breast cancer. Information about the age at first childbirth and other pregnancy-related variables was derived from a questionnaire administered to women during the course of genetic counselling. There was no difference in the mean age at first full-term birth in the cases and controls (24.9 years vs. 24.8 years; P = 0.81, respectively). Compared to women whose first child was born at or before 18 years of age, a later age at first full-term birth did not influence the risk of developing breast cancer (OR = 1.00 per year; 95% CI 0.98-1.03; P-trend = 0.67). Stratification by mutation status did not affect the results. These findings suggest that an early first full-term birth does not confer protection against breast cancer in BRCA mutation carriers. Nonetheless, BRCA mutation carriers opting for a prophylactic oophorectomy as a breast and/or ovarian cancer risk-reducing strategy should complete childbearing prior to age 40 when this prevention modality is most effective.
authors.affiliation: Centre for Research in Women's Health, Women's College Hospital, University of Toronto, Room 750, 790 Bay Street, 7th Floor, Toronto, ON M5G 1N8, Canada.
authors.forename: Joanne
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authors.lastname: Kotsopoulos
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authors.lastname: Lynch
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authors.lastname: Klijn
authors.forename: Parviz
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authors.lastname: Ghadirian
authors.forename: Susan L
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authors.lastname: Neuhausen
authors.forename: Charmaine
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authors.lastname: Eisen
authors.forename: Mary
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authors.lastname: Daly
authors.forename: Beth
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authors.lastname: Karlan
authors.forename: Howard M
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authors.lastname: Saal
authors.forename: Fergus
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authors.lastname: Couch
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authors.lastname: Pasini
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authors.lastname: Wagner
authors.forename: Eitan
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authors.lastname: Friedman
authors.forename: Gad
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authors.lastname: Rennert
authors.forename: Charis
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authors.lastname: Eng
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Weitzel
authors.forename: Ping
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authors.lastname: Sun
authors.forename: Steven A
authors.initials: SA
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authors.initials: B
authors.lastname: Pasche
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authors.forename: W S
authors.initials: WS
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authors.lastname: Lemire
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mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D001943:Breast Neoplasms / Q000453:epidemiology / Q000235:genetics*; D016022:Case-Control Studies; D005260:Female; D019398:Genes, BRCA1; D024522:Genes, BRCA2; D020022:Genetic Predisposition to Disease; D006579:Heterozygote; D006801:Humans; D008875:Middle Aged; D009154:Mutation; D016017:Odds Ratio; D010298:Parity; D011247:Pregnancy; D011252:Pregnancy Complications, Neoplastic; D012042:Registries; D012307:Risk Factors; D013997:Time Factors