First BRCA1 and BRCA2 gene testing implemented in the health care system of Stockholm

The aim of the study was to optimize the criteria for the BRCA1 and BRCA2 g ene testing and to improve oncogenetic counseling in the Stockholm region. Screening for inherited breast cancer genes is laborious and a majority of tested samples turn out to be negative. The frequencies of mutations in the BRCA1 and BRCA2 genes differ across populations. Between 1997 and 2000, 16 0 families with breast and/or ovarian cancer were counseled and screened fo r mutations in the two genes. Twenty-five BRCA1 and two BRCA2 disease-causi ng mutations were found. Various factors associated with the probability of finding a BRCA1 mutation in the families were estimated. Age of onset in d ifferent generations and other malignancies were also studied. Families fro m our region in which both breast and ovarian cancer occur were likely to c arry a BRCA1 mutation (34%). In breast-only cancer families, mutations were found only in those with very early onset. All breast-only cancer families with a mutation had at least one case of onset before 36 years of age and a young median age of onset (< 43 years). Other malignancies than breast an d ovarian cancers did not segregate in the BRCA1 families and surveillance for other malignancies is not needed, in general. Decreasing age of onset w ith successive generations was common and must be taken into account when s urveillance options are considered.