A brief review of the current breast cancer prevention trials and proposals for future trials

The available results from breast cancer chemoprevention trials are review ed. Four trials using tamoxifen have been performed of which three have rep orted efficacy results. A fifth trial using raloxifene has also been publis hed. The largest tamoxifen trial shows approximately a 50% reduction in bre ast cancer incidence in the short term, bur the two smaller trials have not found any incidence reduction. Greater agreement exists for side-effects - thromboembolic disease and endometrial cancers are raised about 2 to 3-fol d when tamoxifen is used for 5 years. The possible reasons for the discrepa ncy in breast cancer reduction are explored. A review of trial parameters d oes not clearly explain this difference, and a meta-analysis indicates that all results are compatible with a 42% reduction in short-term incidence. S everal important questions remain about the clinical implication of this re sult, including the effect on mortality, the appropriate risk groups for ch emoprevention and the long-term effects on incidence. Continued follow-up o f these trials is crucial for resolving these issues. (C) 2000 Elsevier Sci ence Ltd. All rights reserved.