Novel and recurrent BRCA1/BRCA2 mutations in early onset and familial breast and ovarian cancer detected in the Program of Genetic Counseling in Cancer of Valencian Community (eastern Spain). Relationship of family phenotypes with mutation prevalence

During the first 6 years of the Program of Genetic Counselling in Cancer of Valencia (eastern Spain), 310 mutations (155 in BRCA1 and 155 in BRCA2 ) in 1,763 hereditary breast (BC) and ovarian cancer (OC) families were identified. Of the mutations found 105 were distinct (53 in BRCA1 and 52 in BRCA2 ), eight new and 37 recurrent. Two of the novel mutations were frame-shift placed in exons 2 and 11 of BRCA1 and the remaining six were placed in BRCA2 ; four frame-shift (three in exon 11 and one in exon 23), one deletion of the entire exon 19 and one in the intervening sequence of exon 22. The BRCA1 mutations with higher recurrence were c.66_68delAG, c.5123C > A, c.1961delA, c.3770_3771delAG and c.5152+5G > A that covered 45.2 % of mutations of this gene. The age of onset of BCs of c.68_69delAG mutation carriers occurs later than for the other recurrent mutations of this gene (45 vs. 37 years; p = 0.008). The BRCA2 mutations with higher recurrence were c.9026_9030delATCAT, c.3264insT and c.8978_8991del14 which represented 43.2 % of all mutations in this gene, being the most recurrent mutation by far c.9026_9030delATCAT that represents 21.3 % of BRCA2 mutations and 10.6 % of all mutations. Probands with family histories of BC and OC, or OC and/or BC in at least two first degree relatives, were the more likely to have BRCA1/BRCA2 mutations (35.2 % of the total mutations). And that most BRCA1 mutations (73.19 % mutations) occurred in probands with early-onset BC or with family history of OC.