Cancer susceptibility genes. How strong is the evidence?

We consider the case of a 25-year old carrier of the breast cancer susceptibility genes; BRCA1 and BRCA2. On the basis of observed mutations it is believed that the carrier has an 87% chance of developing breast cancer. Currently, the most commonly prescribed treatment is for a double mastectomy. The popularity of this procedure has increased greatly over the last twenty years; so much so that many leading clinics in the U.S. have a waiting list in order to be tested. New genes are being discovered all the time and, many more than just BRCA1 and BRCA2 are believed to be susceptibility genes for breast cancer. It has been suggested that whole populations be screened in order to detect those individuals at increased
risk of particular cancers. This is not feasible at present and the question remains of what action to take following a positive test. In this talk we consider some of the methodology behind this work. Does preventive surgery make sense for a carrier? Does it make any sense to get tested in the first place?