Breast cancer prevention: present and future

Increased risk of breast cancer may result from modifiable factors such as endogenous hormone levels, obesity, HRT, and non-lactation, or non-modifiab le factors such as genetic susceptibility or increasing age. Those factors that are easiest to modify may have a limited impact on the totality of bre ast cancer. The Gail model, based on known factors may be useful for estima ting lifetime risk in some individuals. Tamoxifen prevention still remains contentious. In the NSABP-P I study, there was a 49% reduction in risk of b reast cancer in women given tamoxifen but in the Italian and Royal Marsden trials, no effect on breast cancer incidence was detected, possibly because of the different case-mix in these studies. Raloxifene, tested in the MORE trial reduced the incidence of breast cancer by 65%. The effect was restri cted to ER positive tumours: no reduction in ER negative cancers was seen. Life-style factors such as diet, obesity, exercise, and age of first full t erm pregnancy and number of pregnancies have a mild to moderate impact on r isk and so may have little effect on the incidence of breast cancer. Reduct ion of alcohol intake could lead to a modest reduction in the risk of breas t cancer but possibly adversely affect other diseases. So far, studies of r etinoids have not shown a benefit in terms of breast cancer risk reduction. Fat reduction and GnRH analogues reduce mammographic density but have not yet been shown to affect risk. (C) 2001 Harcourt Publishers Ltd.