P-58 Distribution of Genetic Mutations in Bahamian Patients with Breast Cancer

Methods: Consecutive patients who met the criteria for genetic testing were evaluated using a saliva test. The specimen was processed using Invitae® labs, a College of American Pathologists (CAP)-accredited and Clinical Laboratory Improvements (CLIA)-certified clinical diagnostic laboratory. Full-gene sequencing and deletion/duplication analysis using next generation sequencing technology (NGS) was performed.

Results: Thirty-nine consecutive patients met criteria for genetic testing based on current NCCN guidelines. Their age ranged between 27 to 84 years, and all had histologically proven breast cancer. Eight (20.5%) had no evidence of mutation and 31 (79.5%) had at least one mutation identified. Three (7.7%) patients had three mutations, 10 (25.6%) patients had two mutations, and 18 (46.2%) patients had one mutation (BRCA1=9, ATM=6, AXIN=5, APC=5, SDHA=3, POLE=3, BRCA2=2, KIT=2, MSH3=2, PMS2=2, NBN=1, MSH6=1, MUTYH=1, DITCER1=1, RAD51=1, RAD50=1, BARD1=1, SDHD=1, TP53=1, TSC2=1, PALB2=1). There were seven (14.0%) pathogenic gene mutations, all of which were BRCA mutations; the remaining mutations were variants of undetermined significance (VUS).

Conclusion: Almost half (46.2%) of patients had at least one gene mutation identified. BRCA gene represented all (100.0%) identified pathogenic gene mutations. VUS (43,86.0%) was the most common mutations identified in over 80% of patients. VUS are DNA sequences are not clinically actionable but present a diagnostic challenge to the clinician. These non-informative results increase anxiety among patients and providers. Until the pathogenicity of VUS is determined its role in informing management decisions is limited.