Possible enhancement of the cardiotoxicity of doxorubicin when combined with mitomycin C.

Forty-six patients with recurrent metastatic breast cancer were treated with a combination chemotherapy including doxorubicin and mitomycin C. Myocardial contractility was monitored by means of echocardiography. During therapy there was a progressive deterioration of myocardial function, and this phenomenon was found to be linearly correlated to the cumulative dose of doxorubicin. Six patients (13.8%) developed congestive heart failure during therapy; it occurred after the median cumulative dose of 322 mg/m2 (range 135-472). Possible risk factors of cardiomyopathy could be identified in only two patients. These results suggest that mitomycin C could enhance the cardiotoxicity of doxorubicin.