Audit of BRCA1 and BRCA2 gene mutation detection rate in women with triple negative breast cancer diagnosed under 60 years


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Cecilia Compton1,Rose Sarah1,Izatt Louise1,Ruddy Deborah1,Shaw Adam1,Tripathi Vishakha1,Walsh Cheryl1,Nayanta Sodha1,Anushka Srinivas2,Anju Kulkarni1
1Guy's Hospital,2King's College London Medical School

Abstract

Background

The National Institute for Health and Care Excellence clinical guideline 164 (NICE CG164) recommends BRCA1/2 gene mutation testing is offered to patients with ≥10% mutation carrier probability. The literature suggests women diagnosed with triple negative breast cancer (TNBC) < 50 years meet this threshold but data for women diagnosed between 50 and 60 years of age is inconsistent. The South East Thames Regional Genetics Service has offered BRCA1/2 gene mutation testing to women with a TNBC diagnosis under 50 years since 2013. This audit expanded testing to women diagnosed <60 years to determine if women diagnosed between 50-59 years also meet the 10% NICE CG164 threshold.

Method

Data has been collected prospectively since 1 April 2015 for all women referred to our service with TNBC < 60 years who consented to BRCA1 and BRCA2 gene mutation testing. The data collected includes Manchester Score, Polish/Jewish ancestry, history of other BRCA1/2-related cancers in the family, BRCA1/2 mutation status and whether the patient would have qualified for genetic testing prior to implementing the audit.

Results

181 tests were performed in the first year of data collection with an overall BRCA1/2 gene mutation detection rate of 18%. 70 tests were for women with TNBC diagnosed between 50 and 59 years, 10 of whom qualified for testing based on family history alone. The mutation detection rate was 10% for women diagnosed with TNBC diagnosed between 50 and 59 years, who would not have been offered testing based on family history.

Conclusion

Based on our data, women diagnosed with triple negative breast cancer from 50 to 59 years meet the NICE CG164 10% mutation carrier probability threshold. We, therefore, propose that BRCA1/2 gene mutation testing should be offered to all women diagnosed with TNBC under the age of 60 years irrespective of their family history.