Breast Cancer Research and Treatment

, Volume 131, Issue 2, pp 571–580

Body mass index and risk of second primary breast cancer: The WECARE Study


    • Department of Epidemiology and BiostatisticsMemorial Sloan-Kettering Cancer Center
  • Esther M. John
    • Cancer Prevention Institute of California
  • Lene Mellemkjær
    • Institute of Cancer Epidemiology, Danish Cancer Society
  • Anne S. Reiner
    • Department of Epidemiology and BiostatisticsMemorial Sloan-Kettering Cancer Center
  • Kathleen E. Malone
    • Division of Public Health SciencesFred Hutchinson Cancer Research Center
  • Charles F. Lynch
    • Department of EpidemiologyUniversity of Iowa
  • Jane C. Figueiredo
    • Department of Preventive MedicineUniversity of Southern California
  • Robert W. Haile
    • Department of Preventive MedicineUniversity of Southern California
  • Roy E. Shore
    • Department of Environmental MedicineNew York University
    • Radiation Effects Research Foundation
  • The WECARE Study Collaborative Group
  • Jonine L. Bernstein
    • Department of Epidemiology and BiostatisticsMemorial Sloan-Kettering Cancer Center
  • Leslie Bernstein
    • Division of Cancer Etiology, Department of Population SciencesBeckman Research Institute and City of Hope Comprehensive Cancer Center

DOI: 10.1007/s10549-011-1743-4

Cite this article as:
Brooks, J.D., John, E.M., Mellemkjær, L. et al. Breast Cancer Res Treat (2012) 131: 571. doi:10.1007/s10549-011-1743-4


The identification of potentially modifiable risk factors, such as body size, could allow for interventions that could help reduce the burden of contralateral breast cancer (CBC) among breast cancer survivors. Studies examining the relationship between body mass index (BMI) and CBC have yielded mixed results. From the population-based, case–control, Women’s Environmental, Cancer and Radiation Epidemiology (WECARE) Study, we included 511 women with CBC (cases) and 999 women with unilateral breast cancer (controls) who had never used postmenopausal hormone therapy. Rate ratios (RR) and 95% confidence intervals (CI) were used to assess the relationship between BMI and CBC risk. No associations between BMI at first diagnosis or weight-change between first diagnosis and date of CBC diagnosis (or corresponding date in matched controls) and CBC risk were seen. However, obese (BMI ≥ 30 kg/m2) postmenopausal women with estrogen receptor (ER)-negative first primary tumors (n = 12 cases and 9 controls) were at an increased risk of CBC compared with normal weight women (BMI < 25 kg/m2) (n = 43 cases and 98 controls) (RR = 5.64 (95% CI 1.76, 18.1)). No association between BMI and CBC risk was seen in premenopausal or postmenopausal women with ER-positive first primaries. Overall, BMI is not associated with CBC risk in this population of young breast cancer survivors. Our finding of an over five-fold higher risk of CBC in a small subgroup of obese postmenopausal women with an ER-negative first primary breast cancer is based on limited numbers and requires confirmation in a larger study.


BMISecond primary contralateral breast cancerER-negative



Body mass index


Contralateral breast cancer


Confidence interval






Estrogen receptor


Hazard ratio


Postmenopausal hormone therapy


Odds ratio


Progesterone receptor


Rate ratio


Surveillance, Epidemiology and End Results program


Unilateral breast cancer


Women’s Environmental Cancer and Radiation Epidemiology


World Health Organization

Copyright information

© Springer Science+Business Media, LLC. 2011