One of the present issues being addresses in clinical trials is whether anticancer drugs should be used together (cancer combination chemotherapy) or if they should be used as a single agent (sequential chemotherapy). If drugs are combined and share common toxicity such as bone marrow suppression, often the dosage must be reduced, perhaps also reducing its efficacy. Some drugs in combination may be synergistic, wherein the combination of two or more drugs enhances the anticancer effect as compared to when drugs are given alone in sequence.
Based on successful clinical trial results in the treatment of Hodgkin's disease, breast cancer chemotherapy was traditionally given in combination. Early results did demonstrate a combination of drugs were better than a single agent. As new evidence emerges regarding the presence of potentiation of these drugs and toxicities from interactions, cancer chemotherapy regimens may contain combined drugs, as well as drugs given singularly.
The other major issue for cancer specialists treating breast cancer with chemotherapy is drug dose regimen. The higher the dosage given in a fixed time period, the greater the potential toxicity and risk of adverse effects on the patient. Oftentimes, this is bone marrow toxicity, which involves a suppression of bone marrow stem cells leading to decreased white blood cell production (leucopenia), placing the patient at heightened risk for infection. Research shows that a certain dose intensity must be given to achieve the maximum antineoplastic activity, but going beyond this threshold only increases risk without further benefit.
A majority of anticancer drugs affect all dividing cells in the body. This includes both normal cancer cells. If a woman has microscopic spread of the cancer cells, these cancer cells will be replicating and be more sensitive to chemotherapy than most normal cells. Some of the body's normal cells that also replicate on a regular basis are the bone marrow cells and the lining cells of the gastrointestinal tract. It is for this reason that these normal cells are also sensitive to the anticancer drugs. Presently, there are several drugs that kill breast cancer cells and there are new agents under investigation. Much progress has been made in how to optimally administer these agents and there are supportive therapies to prevent the adverse events of chemotherapy. Several drug combinations have evolved and have been commonly used to treat women for possible metastatic disease. The standard has been one of two combinations: adriamycin and cyclophosphamide with or without 5 fluorouracil; and cyclophosphamide, methotrexate and 5 fluorouracil.
A new agent, trastuzumab (brand name Herceptin), an antibody directed against Her-2 protein that is abundant on the cancer cell surface. This cancer protein is over expressed in cancer cells and poses as a very good target for anticancer agents. This drug is presently undergoing testing for the use in women with localized breast cancer that demonstrate an abundance of this cancer protein.
It is important for cancer patients to educate themselves about chemotherapy and its adverse effects before making a decision to incorporate certain anticancer drugs in their treatment plan.
Michael Russell Your Independent guide to Breast Cancer
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