Familial breast cancer genetic testing in the West of Ireland.

AIMS: The majority of hereditary breast and ovarian cancers are associated with highly penetrant mutations in two genes: BRCA 1 and 2. Our aim was to investigate the prevalence and types of BRCA mutations in patients from the West of Ireland.
METHODS: A retrospective cohort study was undertaken that included all patients from the counties, Mayo, Sligo, Galway, Roscommon, and Clare, who were referred to the National Centre for Medical Genetics (NCMG) for testing for mutations in BRCA 1 or 2 between 2000 and 2010. Data including age, symptoms, family history, Manchester score, and test results were recorded and analysed using SPSS.
RESULTS: The NCMG received 380 referrals from the Western seaboard, including 148 for diagnostic testing and 232 for predictive evaluation. Sixty-five patients did not attend for assessment. Two hundred and fifty-six patients fulfilled criteria for genetic counselling, which was accepted by 184, of whom 127 proceeded to testing. Predictive tests were more often declined than diagnostic [41 (46 %) vs. 16 (17 %)]. Ten mutations in BRCA 1 were identified in 20 patients (15 families), including Exon 1-23del (3 families); Exon 14-20del (2 families) and E143X (2 families). Six mutations in BRCA 2 were identified in 15 patients (12 families) including 8525delC (n = 2 families) and 8205-1G>C (n = 3 families). Patients with positive results had significantly higher Manchester scores than those with negative tests [median 25.5 (12-48) vs. 20 (8-37), p = 0.042, Mann-Whitney U test].
CONCLUSION: To identify patients with highly penetrant variants, referrals should be made with strict adherence to guidelines. Counselling should be individualised to counteract intrinsic psychological barriers to testing.