Interaction between Doxorubicin and Mitomycin C on Mortality and Myocardial Contractility in Guinea PIG

Cardiac and cardiovascular toxicity of nonanthracycline anticancer drugs

Anthracyclines are a well-known cause of cardiotoxicity, but a number of other drugs used to treat cancer can also result in cardiac and cardiovascular adverse effects. Cardiotoxicity can result in the alteration of cardiac rhythm, changes in blood pressure and ischemia, and can also alter the ability of the heart to contract and/or relax. The clinical spectrum of these toxicities can range from subclinical abnormalities to catastrophic life-threatening, and sometimes fatal, sequelae. These events may occur acutely or may only become apparent months or years following completion of oncological treatment. Ischemia and rhythm abnormalities are treated symptomatically in most cases. Knowledge of these toxicities can aid clinicians to choose the optimal and least toxic regimen suitable for an individual patient.

Cardiotoxicity of mitomycin A, mitomycin C, and seven N7 analogs in vitro

The alkylating antitumor agents mitomycin A (MMA), mitomycin C (MMC), and seven N7 analogs were compared in terms of their cardiotoxic and antitumor activity in vitro. Neonatal rat-heart myocytes were sensitive to five of the compounds studied, including MMA, 7-dimethylamidinomitosane (BMY-25282), 7-(N-methyl-piperazinyl)-mitosane (RR-194), N7-(4-iodophenyl)-MMC (RR-208), and N7-(4-hydroxyphenyl)-MMC (M-83) in order of descending molar potency. MMA and RR-208 possessed the greatest cytotoxic potency against 8226 human myeloma tumor cells in vitro. Two of the nine mitomycins studied, BMY-25282 and M-83, showed greater cytotoxic potency for heart cells. For these two agents, the ratio of the 50% inhibitory concentration in heart cells to that in 8226 myeloma cells was 50 and 32, respectively. For the other analogs, the tumor-cell cytotoxic potency was much higher (ranging from 200 to 7,000). For the nine mitomycin compounds, a correlation was found between heart-cell toxicity and low reduction potentials (E1/2 values) ranging from -0.16 to -0.37 V. Thus, as the reduction potential decreased (easier reducibility), the cardiotoxic potency in vitro increased (r = 0.81). In contrast, mitomycins with reduction potentials of higher than -0.37 V were much less potent cardiotoxins. Thus, mitomycin C (E1/2 = -0.45 V) was noncardiotoxic even when tested at concentrations 100-fold above those pharmacologically achievable in humans. Mitomycin C also failed to enhance doxorubicin (Adriamycin) cardiotoxicity in vitro. Importantly, no correlation was found between the reduction potential and the antitumor activity of the nine analogs (n = 0.51), in this small series.

A prospective study on the dose dependency of cardiotoxicity induced by mitomycin C

Since 1975 mitomycin C (MMC) has been suggested to be cardiotoxic, especially when combined with or given following doxorubicin. Data on dose dependency or incidence concerning this side effect were not known. We have initiated a prospective study to obtain some more data on these subjects. Forty-four MMC-treated patients were studied, 37 of them could be evaluated. All patients were studied by repeated physical examinations, chest X-rays, electro- and echocardiography and radionuclide left ventricular ejection fraction (EF) determinations. The results were evaluated per cumulative dose level. One of the patients developed cardiac failure after 30 mg m-2 MMC and only 150 mg m-2 doxorubicin. The cardiac failure was predicted by a drop in EF determined during a cold pressor test. None of the other patients developed clinical cardiotoxicity, nor did the studied parameters change. The literature on this subject was also reviewed. Based on the combined data from the present study and the literature, we suggest that MMC-related cardiotoxicity is dose dependent, occurring at cumulative dose levels of 30 mg m-2 or more, mainly in patients also (previously or simultaneously) treated with doxorubicin. The incidence is likely to be less than 10% even for this risk group.

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.