Table 1

 Sex ratio in BRCA1 carriers, BRCA2 carriers, and non-carriers

GroupProbandsNumber of offspringM:F Ratiop valueReference
*Ashkenazi Jewish women tested for founder germline mutations in BRCA1 and BRCA2 at one of the McGill University affiliated hospitals, Montreal, Canada between 1996 and 2003, as part of clinical service. BRCAPRO scores for BRCA1 carriers ranged from 0.018 to 0.923 with a median of 0.48. The BRCA2 positive pedigrees were found to have scores that ranged from 0.094 to 0.984 with a median of 0.46. It is highly likely that women with female children are over-represented in this study population.9,10
†Ashkenazi Jewish women from six oncology centres in Toronto and Montreal who had been diagnosed with breast cancer before 1 May 1998, as part of a study designed to determine the frequency and penetrance of founder mutations.6
‡Ashkenazi Jewish women from 11 medical centres in North America and Israel who had been diagnosed with ovarian cancer and were tested for the founder mutations to examine the familial risks and estimate the proportion of ovarian cancers associated with these mutations.7
§Women of various ethnicities were recruited into a Familial Ovarian Tumor Study through the Ontario Cancer Registry.5
¶Norwegian series of 615 consecutive ovarian cancers patients who consented to genetic testing were initially screened for the two most frequent local mutations described in Dorum et al8 and two additional mutations (3347delAG and 816delGT). All patients with relatives affected with breast and/or ovarian cancers were later subjected to extensive mutation search in BRCA1 and BRCA2 with various methods. Altogether 37 truncating mutations were found (36 in BRCA1, one in BRCA2), indicating a prevalence of 6.0% of BRCA1/2 carriers in ovarian cancers in the total series, 18/171 (10.5%) < 50 years of age, 18/300 (6%) at 50–70 years, and 1/144 (0.7%) at 70+ years. Only the data for BRCA1 are presented here.
BRCA1 mutation carriers
    AJ McGill University clinic*4553501.060.77
    AJ breast cancer study†3433360.920.72 6
    AJ ovarian cancer study‡5737560.660.05 7
    Ontario ovarian tumour study§5756551.020.92 5
    Norway ovarian cancer study¶3642371.140.57 8
BRCA2 mutation carriers
    AJ McGill University clinic178190.420.03
    AJ breast cancer study1512111.090.83 6
    AJ ovarian cancer study2930330.910.71 7
    Ontario ovarian tumour study4357451.270.23 5
BRCA1/2 non-carriers
    AJ McGill University clinic1981812190.830.06
    AJ breast cancer study3643924060.960.62 6
    AJ ovarian cancer study1221291400.920.50 7
    Ontario ovarian tumour study2340271.480.11 5