Prevention of breast cancer: current state of the science and future opportunities

Despite significant progress in breast cancer treatment, mammary tumours still represent the second most frequent cause of cancer-related death in women in the US, with > 211,000 new cases in 2005; however, an expanding range of options for early diagnosis and more reliable risk assessment offers new alternatives for disease control by cancer prevention. Completed large studies with the classical selective estrogen receptor modulator (SERM) tamoxifen have demonstrated that preventing breast cancer pharmacologically is now possible. Novel SERMs, aromatase inhibitors and gonadotropin-releasing hormone agonists targeting hormonal pathways are being tested in clinical trials, revealing the potential for dramatic reductions in tumour incidence with minimal side effects; however, SERMs and aromatase inhibitors are effective only against estrogen receptor-positive tumours, thus chemopreventive drugs targeting other critical signalling pathways (such as retinoids, selective COX inhibitors and tyrosine kinase inhibitors) may provide a means to prevent estrogen receptor-negative breast cancer. In the future, hormonal and estrogen receptor-independent agents may be combined to prevent the development of all mammary tumours. This article reviews the current and novel strategies for breast cancer prevention.