Cascade screening in BRCA1/2 mutation carriers

Genetic counselling for families with BRCA1 & 2 has been available in Ireland since 1998. We describe the follow-on cascade from the initial 29 index cases that tested positive for either gene. 28 of the index cases were female and 1 was male. Their combined sibship and offspring totalled 125 and 129 respectively. Of the 125 siblings, 21/72 (29%) females and 10/53 (19%) males came forward for counselling and all were tested. Of the 129 at risk offspring, 56 (43%) [25 females and 31 males] were over 18 years and therefore were eligible for testing. 20/25 (80%) females and 6/31 (19%) males came for counselling and all bar one female was tested. In summary, 31/125 (25%) at risk siblings were tested and 25/56 (45%) offspring were tested. Only one person, a daughter of an affected individual who attended clinic, declined testing. The remaining 197 (77%) individuals have not come forward for counselling. Our results suggest that a) there is a low-moderate testing rate in Ireland when compared to other European centres; and that b) daughters of BRCA1/2 carriers are more likely to come forward for testing than female siblings. Specific factors which appeared to influence attendance included poor dissemination of information among families about the test; and lower levels of communication among siblings than within the nuclear family.