New research shows that women at high risk for breast cancer are also at high risk for heart disease. Most women with hereditary breast and ovarian cancer are susceptible to mutations in BRCA1 or BRCA2, genes that normally inhibit the growth of breast and ovarian tumors. Dr. Subodh Verma, a cardiac surgeon at St. Michael’s Hospital, said his research team was surprised to find that the two genes also regulate heart function. With a heart attack, mice with the BRCA1 gene mutation had a mortality rate that was three to five times higher. Most of this was due to strong heart failure, probably because they suffered twice as many heart attacks as mice without the gene mutation. Heart failure can be observed in mice with mutations in the BRCA1 or BRAC2 genes due to the double shock, a condition that can be treated with adriamycin, the most common chemotherapy drug used to treat breast cancer. In addition, studies in mice have been validated by observations in human tissue. The researchers are convinced that the mutated BRCA1/2 gene inhibits DNA repair within myocytes, which is essential for recovery from a heart attack, and Dr. Verma said, “Our study suggests that those at risk for breast cancer may also be at risk for a previously unknown heart condition. More importantly, we now know that breast cancer and heart disease (the two leading causes of death in Canadian women) share a common biological basis and a common domain. Dr. Verma emphasizes that these studies may be an important implication for patients. Knowing that the BRCA1/2 gene is essential for DNA repair may lead to future treatments for heart disease (a major cause of death in humans). Women who carry this mutated gene now know that they are at risk for heart disease in addition to a high risk of developing cancer. Dr. Christine Brezden-Masley, an oncologist at St. Michael’s Hospital and co-author of the article, said that while internists know that adriamycin is associated with heart failure, the new study shows that women with the BRCA1/2 mutation are particularly sensitive to its toxicity. “This means that when a patient has the mutated gene, I now have to think about what dose I’m going to prescribe for them, or whether we should consider a different treatment regimen.”