Impact of teenage oral contraceptive use in a population-based series of early-onset breast cancer cases who have undergone BRCA mutation testing

• Published in: European journal of cancer (1990) Vol. 41; no. 15; pp. 2312 - 2320
• Main Authors: Jernström, Helena, Loman, Niklas, Johannsson, Oskar T., Borg, Åke, Olsson, Håkan
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-10-2005; Elsevier
• Subjects: Adolescent; Adult; Biological and medical sciences; BRCA1/2; Breast Neoplasms - chemically induced; Breast Neoplasms - genetics; Cancer and Oncology; Cancer och onkologi; Carcinoma, Ductal, Breast - chemically induced; Carcinoma, Ductal, Breast - genetics; Clinical Medicine; Contraceptives, Oral - adverse effects; Early-onset breast cancer; Epidemiologic Methods; family; Family history; Female; Genes, BRCA1; Genes, BRCA2; Genetic Testing - methods; history; Humans; Klinisk medicin; Medical and Health Sciences; Medical sciences; Medicin och hälsovetenskap; Mutation - genetics; Oral contraceptives; Pharmacology. Drug treatments; Population-based case-control study; Sweden - epidemiology; Tumors; Sweden; BRCA1/2; Early-onset breast cancer; Oral contraceptives; Family history; Population-based case-control study; Human; Oral administration; Breast cancer; Malignant tumor; Case control study; Medical screening; Mammary gland diseases; Family story; Cancerology; Age of onset; Adolescent; Genetics; Contraceptive; Mutation; BRCA1 gene; Antecedent; Tumor suppressor gene
• ISSN: 0959-8049; 1879-0852; 1879-0852
• DOI: 10.1016/j.ejca.2005.03.035

Oral contraceptive (OC) use in young women has been associated with an increased risk of breast cancer. This matched case-control study aims to elucidate the combined effects of OC use and genetic factors in a population-based series of BRCA1/2 mutation-tested early-onset breast cancers. A first invasive breast cancer was diagnosed in 259 women aged ⩽40 years between 1990 and 1995 in the South Swedish Health Care Region. A total of 245 women were included in this study. Information on family history of cancer, reproductive factors, smoking and OC use was obtained from questionnaires or patient charts. Three age-matched controls per case were chosen from a prospective South Swedish cohort. Ever OC use and current OC use were not associated with breast cancer. Cases were more likely to have used OCs before age 20 years (adjusted odds ratio (OR) 2.10 (95% CI 1.32–3.33)) and before their first child (adjusted OR 1.63 (95% CI 1.02–2.62)). When stratified by age, the effect of early OC use was limited to women diagnosed prior to age 36 years (OR 1.53 (1.17–1.99) per year of OC use prior to age 20 years). The risks were similar for low-dose and high-dose OCs. The probability of being a BRCA1/2 mutation carrier was three times higher among cases who started OC use prior to age 20 years compared with cases who started at age 20 years or older or who had never used OCs. However, the duration of OC use was similar among cases with and without BRCA1/2 mutations. No association was seen with a first-degree family history of breast cancer. Each year of OC use prior to age 20 years conferred a significantly increased risk for early-onset breast cancer, while there was no risk associated with use after age 20 years.