Research article

Breast Cancer Research

, 14:R42

Open Access This content is freely available online to anyone, anywhere at any time.

Breastfeeding and the risk of breast cancer in BRCA1 and BRCA2 mutation carriers

  • Joanne KotsopoulosAffiliated withFamilial Breast Cancer Unit, Women’s College Research Institute
  • , Jan LubinskiAffiliated withHereditary Cancer Center, Pomeranian Medical University
  • , Leonardo SalmenaAffiliated withFamilial Breast Cancer Unit, Women’s College Research Institute
  • , Henry T LynchAffiliated withDepartment of Preventive Medicine and Public Health, Creighton University School of Medicine
  • , Charmaine Kim-SingAffiliated withBC Cancer Agency
  • , William D FoulkesAffiliated withPrograms in Cancer Genetics, Department of Oncology and Human Genetics, McGill University
  • , Parviz GhadirianAffiliated withEpidemiology Research Unit, Research Center of the University of Montreal Hospital Centre (CRCHUM)
  • , Susan L NeuhausenAffiliated withDepartment of Population Sciences, Beckman Research Institute of City of Hope
  • , Rochelle DemskyAffiliated withDivision of Gynecologic Oncology, Department of Obstetrics and Gynecology, University of Toronto
    • , Nadine TungAffiliated withBeth Israel Deaconess Hospital
    • , Peter AinsworthAffiliated withLondon Regional Cancer Program
    • , Leigha SenterAffiliated withDivision of Human Genetics, The Ohio State University Medical Center, Comprehensive Cancer Center
    • , Andrea EisenAffiliated withToronto-Sunnybrook Regional Cancer Center
    • , Charis EngAffiliated withGenomic Medicine Institute and Center for Personalized Genetic Healthcare, Cleveland Clinic
    • , Christian SingerAffiliated withDepartment of Obstetrics and Gynecology and Comprehensive Cancer Center, Medical University of Vienna
    • , Ophira GinsburgAffiliated withFamilial Breast Cancer Unit, Women’s College Research InstituteDepartment of Medicine, University of Toronto
    • , Joanne BlumAffiliated withBaylor University Medical Center, Hereditary Cancer Risk Program
    • , Tomasz HuzarskiAffiliated withHereditary Cancer Center, Pomeranian Medical University
    • , Aletta PollAffiliated withFamilial Breast Cancer Unit, Women’s College Research Institute
    • , Ping SunAffiliated withFamilial Breast Cancer Unit, Women’s College Research Institute
    • , Steven A NarodAffiliated withFamilial Breast Cancer Unit, Women’s College Research Institute Email author 
    • , the Hereditary Breast Cancer Clinical Study Group

Abstract

Introduction

Breastfeeding has been inversely related to breast cancer risk in the general population. Clarifying the role of breastfeeding among women with a BRCA1 or BRCA2 mutation may be helpful for risk assessment and for recommendations regarding prevention. We present an updated analysis of breastfeeding and risk of breast cancer using a large matched sample of BRCA mutation carriers.

Methods

We conducted a case-control study of 1,665 pairs of women with a deleterious mutation in either BRCA1 (n = 1,243 pairs) or BRCA2 (n = 422 pairs). Breast cancer cases and unaffected controls were matched on year of birth, mutation status, country of residence and parity. Information about reproductive factors, including breastfeeding for each live birth, was collected from a routinely administered questionnaire. Conditional logistic regression was used to estimate the association between ever having breastfed, as well as total duration of breastfeeding, and the risk of breast cancer.

Results

Among BRCA1 mutation carriers, breastfeeding for at least one year was associated with a 32% reduction in risk (OR = 0.68; 95% CI 0.52 to 0.91; P = 0.008); breastfeeding for two or more years conferred a greater reduction in risk (OR = 0.51; 95% CI 0.35 to 0.74). Among BRCA2 mutation carriers, there was no significant association between breastfeeding for at least one year and breast cancer risk (OR = 0.83; 95% CI 0.53 to 1.31; P = 0.43).

Conclusions

These data extend our previous findings that breastfeeding protects against BRCA1-, but not BRCA2-associated breast cancer. BRCA mutation carriers should be advised of the benefit of breastfeeding in terms of reducing breast cancer risk.