Progress in Systemic Chemotherapy of Primary Breast Cancer: an Overview

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Abstract
Substantial progress has been made in the multidisciplinary management of primary breast cancer during the last 30 years. Adjuvant chemotherapy has been shown to significantly reduce the annual risk of cancer recurrence and mortality, and these effects persist even 15 years after diagnosis. Combination chemotherapy is superior to single-agent therapy and anthracycline-containing regimens. Those that combine an anthracycline with 5-fluorouracil and cyclophosphamide are more effective than regimens without an anthracycline. Six cycles of a single regimen appear to provide optimal benefit. Dose reductions below the standard range are associated with inferior results. Dose increases that require growth factor or hematopoietic stem cell support are under investigation; at this time, the existing results provide no compelling reason to use this strategy outside a clinical trial. Regimens using fixed crossover designs with two non-cross-resistant regimens are being evaluated. The addition of a taxane to anthracycline-containing regimens is currently under intense scrutiny, and preliminary analysis of the first three clinical trials has shown encouraging, albeit not compelling, results. For patients with estrogen receptor-positive breast cancer, the sequential administration of chemotherapy and 5 years of tamoxifen therapy provides additive benefits. No compelling evidence exists to combine ovarian ablation with chemotherapy. Most side effects and toxic effects are self-limited, although premature menopause requires monitoring and preventive interventions to preserve bone mineral density. The small risk of acute leukemia is of concern, and additional research to develop safer regimens is clearly indicated. The overall effect of optimal local/regional treatment combined with an anthracycline-containing adjuvant chemotherapy and a taxane (and, for patients with estrogen receptor-positive tumors, 5 years of tamoxifen therapy) is a greater than 50% reduction in annual risks of recurrence of and death from breast cancer. For most patients at intermediate or high risk of cancer recurrence, the benefits of adjuvant chemotherapy exceed by far its unwanted effects.