We must not forget that all cancers are ultimately determined by a combination of genetic and environmental factors and the interplay of these is one of our most urgent subjects for research. The problem of statistical prediction becomes especially worrying when irreversible decisions are based on it. The question of whether to have prophylactic mastectomies or oophorectomies for carriers of BRCA mutations is a particularly difficult one. Estimated gains in life expectancy decline with age, however. Gains would be minimal for a 60 year old, less than one year on average, very little more than the estimated gain in life expectancy of 8 months for a woman without a mutation.
Risks associated with surgery are immediate.
The reported gain in life expectancy applies only to women who already know they have the gene mutations. Screening to find the mutation would carry its own demerits - not least those of false positive or false negative results in circumstances where prevalence may not be high. So this information should encourage a conservative approach to prophylactic surgery. But patients are individuals rather than units of a statistical study and each needs to be given individual consideration. Where this involves changes in genes which predispose to breast cancer this means access to experts who themselves are in possession of the latest information and are able to communicate this in a digestible form to worried people who do not understand the science or statistics.