Doxorubicin and other anthracyclines are an important class of agents for the treatment of early and advanced stage breast cancer, but produce substantial acute and chronic toxicities. One strategy for reducing anthracycline-associated toxicity is packaging them in liposomes. Liposomes are closed vesicular structures that envelop water-soluble molecules. They may serve as vehicles for delivering cytotoxic agents more specifically to tumor, and limit exposure of normal tissues to the drug. Liposomal anthracyclines are more effective and less toxic in a number of preclinical models compared with conventional anthracyclines. Several liposomal anthracyclines have been extensively studied in humans with a variety of cancer types, including TLC D-99 (Myocet; The Liposome Company, Elan Corporation, Princeton, NJ), liposomal daunorubicin (Daunoxome; NeXstar Pharmaceuticals, Inc, San Dimas, CA), and pegylated liposomal doxorubicin (Doxil; Alza Pharmaceuticals, Palo Alto, CA, Caelyx; Schering Corporation, Kenilworth, NJ). Although none of these agents are currently approved for the treatment of breast cancer in the United States, the liposomal doxorubicin preparations seem to have comparable activity and less cardiac toxicity than conventional doxorubicin. Furthermore, they have been safely combined with other cytotoxic agents, including cyclophosphamide, 5-fluorouracil, vinorelbine, paclitaxel, and docetaxel. Further studies will be required do determine their role in the treatment of breast cancer.
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