Contralateral breast cancer risk in BRCA1 and BRCA2 mutation carriers.
This work consists of six parts based on seven manuscripts dealing with some aspects of genetic counselling for BRCA1 mutation carriers. It was demonstrated that the risk of breast and ovarian cancer in first-degree relatives of BRCA1 mutation carriers depends on the type of mutation and is higher in the younger generation. It was also shown that risk of breast cancer, but not of ovarian cancer, is related to cancer type of the proband. These factors should be taken into account when assessing risk of breast and ovarian cancer in relatives of BRCA1 mutation carriers. It was observed that longer breast-feeding, physical activities delaying menarche, preventive oophorectomy, administration of tamoxifen to patients with intact genital tract, and use of contraceptives reduce the risk of breast and ovarian cancer. All these possibilities should be presented to BRCA1 mutation carriers within the framework of cancer risk reduction options. It was also observed that there may be some preference in transmission of the mutant allele to female offspring of BRCA1 founder mutation carriers. Environmental factors appear also to interfere with transmission. The male to female ratio in offspring of BRCA1 mutation carriers is the same as for the general population. As for the consequences of simplified two-stage genetic counselling, the first psychological reaction of a female to the fact that she is a carrier of the BRCA1 mutation is negative. However, understanding that the risk of cancer is high persuades the woman to embrace preventive options. 98% of BRCA1 mutation carriers disclosed during population screening initiated and promoted by the media are convinced of the value of genetic testing. Simplified two-stage genetic counselling appears to be a useful approach promoting increased turnout for BRCA1 mutation testing.