For many years it was acceptable practice to treat breast cancer with only one type of drug. Single agents including 5-fluorouracil, cyclophosphamide, and melphalan were shown to improve disease-free survival rates over surgery alone. Still, none of the clinical trials using single agents resulted in uniform improvement in the overall survival rates of breast cancer patients. In contrast, clinical trials using combination chemotherapy have demonstrated consistent improvement in both disease-free and overall survival rates for premenopausal patients, and modest improvement for postmenopausal patients.

It is now known that the use of several drugs together is more effective than one drug alone in eliminating the cancer. Because each type of drug works on cancer cells in a different way, when the drugs are used together there is a greater chance that if some cells have escaped the lethal effects of one drug, they will succumb to the toxicity of the other agents. Some drug combinations therefore have a synergistic effect. In other words, the combination of drugs works better at killing the cancer cells than the additive effect of the individual drugs.

Combination chemotherapy may also limit the side effects generated by one drug alone. The side effects of some drugs depend on the total dosage. Combination therapy permits lower doses of each individual drug, thus reducing the potential for dose-dependent side effects.

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Cancer