Future possibilities in the prevention of breast cancer: breast cancer prevention trials.
The available results from breast cancer chemoprevention trials are reviewed. Four trials using tamoxifen have been performed, of which three have reported efficacy results. A fifth trial using raloxifene has also been reported. The largest tamoxifen trial showed approximately 50% reduction in breast cancer incidence in the short term, but the two smaller trials did not find any reduction. Greater agreement exists for side effects; incidences of thromboembolic disease and endometrial cancers are raised approximately threefold when tamoxifen is used for 5 years. The possible reasons for the discrepancy in breast cancer reduction are explored. A review of trial parameters does not clearly explain this difference, and a meta-analysis indicates that all results are compatible with a 40% reduction in short-term incidence. Several important questions remain regarding the clinical implications of this result, including the effect on mortality, the appropriate risk groups for chemoprevention and the long-term effects on incidence. Continued follow up of these trials is crucial for resolving these issues.
Department of Methematics, Statistics and Epidemiology, Imperial Cancer Research Fund, London, UK. cuzick@icrf.icnet.uk
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D000328:Adult; D000368:Aged; D016588:Anticarcinogenic Agents / Q000009:adverse effects / Q000627:therapeutic use*; D015519:Bone Density / Q000187:drug effects; D001943:Breast Neoplasms / Q000737:chemistry / Q000453:epidemiology / Q000235:genetics / Q000517:prevention & control*; D002986:Clinical Trials as Topic / Q000706:statistics & numerical data; D016889:Endometrial Neoplasms / Q000139:chemically induced; D020847:Estrogen Receptor Modulators / Q000009:adverse effects / Q000627:therapeutic use*; D005260:Female; D005544:Forecasting; D020249:Hormone Replacement Therapy; D006801:Humans; D015994:Incidence; D008593:Menopause; D015201:Meta-Analysis as Topic; D008875:Middle Aged; D009363:Neoplasm Proteins / Q000032:analysis; D010349:Patient Compliance; D020849:Raloxifene Hydrochloride / Q000009:adverse effects / Q000627:therapeutic use*; D016032:Randomized Controlled Trials as Topic; D011960:Receptors, Estrogen / Q000032:analysis; D012306:Risk; D012307:Risk Factors; D013629:Tamoxifen / Q000009:adverse effects / Q000627:therapeutic use*; D013923:Thromboembolism / Q000139:chemically induced; D016896:Treatment Outcome
D016588:Anticarcinogenic Agents; D020847:Estrogen Receptor Modulators; D009363:Neoplasm Proteins; D011960:Receptors, Estrogen; D013629:Tamoxifen; D020849:Raloxifene Hydrochloride