Diabetes and breast cancer among women with BRCA1 and BRCA2 mutations


  • Other members of the Hereditary Breast Cancer Clinical Study Group are: Henry T. Lynch, Andrea Eisen, Wendy McKinnon, Marie Wood, Howard Saal, Ab Chudley, Andre Robidoux, Charmaine Kim-Sing, Nadine Tung, Susan Armel, Tomasz Huzarski, Diane Provencher, Edmond Lemire, Anna Tulman, Marcia Llacuachaqui, Kevin Sweet, Dawna Gilchrist, Beth Karlan, Raluca Kurz, Barry Rosen, Rochelle Demsky, Seema Panchal, Fergus Couch, Christine Elser, Siranoush Manoukian, Mary Daly, Cezary Cybulski, Jacek Gronwald, Tomasz Byrski, Olufunmilayo Olapade, Dominique Stoppa-Lyonnet, Jeffrey Weitzel, Jane McLennan, Wendy Meschino, Barbara Pasini, Christian Singer, Catharina Dressler, Kelly Metcalfe, Susan Domchek, and Claudine Isaacs.



Hyperinsulinemia and the metabolic syndrome are both risk factors for breast cancer. It is not clear if diabetes is associated with the risk of breast cancer in women with a BRCA1 or BRCA2 mutation.


The authors reviewed the medical histories of 6052 women with a BRCA1 or BRCA2 mutation, half of whom had been diagnosed with breast cancer. They estimated the odds ratio for breast cancer, given a self-report of diabetes. They then estimated the hazard ratio for a new diagnosis of diabetes associated with a history of breast cancer.


There was no excess of diabetes in the period before the diagnosis of breast cancer, compared with controls with no diagnosis of breast cancer. The risk of diabetes was doubled among BRCA carriers in the 15-year period after the diagnosis of breast cancer (relative risk, 2.0; 95% confidence interval [CI], 1.4-2.8; P = .0001), compared with carriers without cancer. The risk was particularly high for women with a body mass index (BMI) >25.0 kg/m2 (odds ratio, 5.8; 95% CI, 4.0-8.6; P = .0001).


After a diagnosis of breast cancer, women with a BRCA1 or BRCA2 mutation face a 2-fold increase in the risk of diabetes, which is exacerbated by a high BMI. Cancer 2011. © 2010 American Cancer Society.