[Chemoprevention of breast cancer: exemestane ready to be tested in study setting]

Prevention of breast cancer is difficult, as most risk factors are difficult to control. Therefore, we have not been able to stop breast cancer incidence rates from rising over past decades. Chemoprevention using aromatase inhibitors, such as exemestane, may change this situation. Aromatase inhibitors are very effective and safe in preventing recurrent disease in postmenopausal breast cancer. A recent randomised placebo-controlled trial showed that in healthy women at moderately increased risk of breast cancer, use of exemestane over a 3-year period reduced the risk of breast cancer by 65%. The reduction was from 0.55% to 0.19% per year, with no adverse events or measurable effect on quality of life. If confirmed by larger studies with longer duration of follow-up, preventive use of exemestane may turn out to be the first acceptable alternative for women at increased risk of developing breast cancer. On a population level, implementation of prevention using aromatase inhibitors has the potential to reduce the incidence of breast cancer. However, currently in the Dutch population, 140 women would need to use exemestane for three years in order to prevent one invasive breast tumour. Therefore, large-scale implementation of exemestane is not advised, but the evidence is sufficient to start studies with exemestane.