Study of the Effect of Eplerenone on Heart Function in Women Receiving Anthracycline Chemotherapy for Breast Cancer

Doxorubicin and other anthracyclines are commonly used to treat breast cancer and other types of cancer. Unfortunately, they can cause heart muscle damage, resulting in scarring, abnormal contraction and relaxation, and heart failure symptoms. This side effect occurs more frequently at higher doses, and limits the total dose that can be given to cancer patients. Eplerenone is an oral medication that prevents or reverses heart damage in other disease states, and is commonly used to treat heart failure. This study will investigate the use of eplerenone to protect the heart from these harmful side effects of doxorubicin. Few therapies have been shown to prevent heart damage in patients receiving anthracyclines. Small studies have suggested that other heart failure medications (ACE inhibitors, beta-blockers) may reduce the incidence of cardiac toxicity, but eplerenone and other drugs in its class (aldosterone antagonists) have not previously been studied. Eplerenone inhibits enzyme pathways that cause scarring of the heart, and animal studies suggest that anthracyclines cause damage through these same pathways. This study aims to investigate whether eplerenone protects the heart from the harmful effects of doxorubicin chemotherapy. Specifically, it will measure the effect that eplerenone has on heart muscle relaxation. It will randomly assign women undergoing chemotherapy with doxorubicin to one of two groups: one group will receive eplerenone, and the other group will receive placebo (sugar) pills. The subjects will not know which type of pills they are taking. Heart muscle relaxation will be measured at baseline, after completion of chemotherapy (8-12 weeks), and after 6 months. There will also be various blood tests measured in the study subjects, to determine whether there might be certain blood tests that identify patients at particularly high risk of heart toxicity after doxorubicin therapy.