Oral contraceptive use and breast cancer risk: A cohort study of BRCA1 and BRCA2 mutation carriers

Research output: Contribution to journalPublished meeting abstract

Abstract

Background: BRCA1 and BRCA2 mutation carriers are at high risk of breast and ovarian cancer. Oral contraceptive preparations (OCPs) may reduce ovarian cancer risk, but its effect on breast cancer risk remains unclear. Methods: Combined data from three cohorts of 5705 BRCA1 and 3521 BRCA2 mutation carriers (IBCCS, BCFR and kConFab) were analyzed using age-dependent Cox regression models stratified for study and birth cohort. We conducted the first prospective analyses on this topic. Our additional main retrospective analyses were leftcensored 5 years preceding date of baseline questionnaire to control for survival bias. The full-cohort retrospective analyses, without left-censoring, was performed to compare results with the literature. Prospective analyses were considered most valid, while retrospective analyses were most powerful. Results: For BRCA1 mutation carriers we found no association between ever OCP use and risk of breast cancer in the prospective analyses (HR=1.08, 95% CI 0.75-1.56), but 23% and 27% increased risks for ever OCP use in the left-censored and full retrospective analyses, respectively. Retrospectively, an increasing trend for longer duration of use, especially before first full-term pregnancy (FFTP) was found (left-censored analyses: 10 years HR 1.41 (95%CI 1.10-1.813), p-trend=0.001 for duration of use before FFTP). For BRCA2 mutation carriers we found a positive association between ever OCP use and risk of breast cancer prospectively (HR=1.75, 95% CI 1.03-2.97), but retrospectively findings were inconsistent (HR=1.06, 95% CI 0.85-1.33 and HR=1.52, 95% CI 1.28-1.81 for the left-censored and full analyses, respectively). Conclusion: For BRCA1 mutation carriers the discrepancy between results of prospective and retrospective analyses may be explained by time since last OCP use before FFTP. Thus, a temporal increased risk of breast cancer following longer duration of OCP use before FFTP cannot be ruled out. The discordant findings between prospective and retrospective analyses for BRCA2 carriers could not be explained. Because of the lack of scientific clarity it is too early to give an unequivocal advice on OCP use with respect to breast cancer risk to BRCA1 and BRCA2 mutation carriers.

Details

Authors
  • L Schrijver
  • Olsson H.
  • A Antoniou
  • R Milne
  • K Phillips
  • N Andrieu
  • D Easton
  • D Goldgar
  • C Engel
  • K Kast
  • M-J Blom
  • T Mooij
  • J Hopper
  • F Van Leeuwen
  • M Terry
  • M Rookus
Organisations
External organisations
  • Netherlands Cancer Institute
  • University of Cambridge
  • University of Melbourne
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Cancer and Oncology

Keywords

  • BRCA1 protein, BRCA2 protein, endogenous compound, oral contraceptive agent, adverse drug reaction, age, breast cancer, cancer risk, cancer survival, case report, cohort analysis, female, gene mutation, genetic susceptibility, human, oral contraceptive use, pregnancy, proportional hazards model, prospective study, questionnaire, retrospective study, side effect
Original languageEnglish
Article numberAbstract 4276
JournalCancer Research
Volume77
Issue number13 Suppl 1
Publication statusPublished - 2017
Publication categoryResearch
Peer-reviewedYes
EventAmerican Association for Cancer Research (AACR) 108th Annual Meeting 2017 - Washington, DC, United States
Duration: 2017 Apr 12017 Apr 5