Multigene panel testing results in patients with multiple breast cancer primaries

Currently, the NCCN guidelines recommend testing of BRCA1 and BRCA2 for females with multiple breast primaries, if her first diagnosis was ≤50 years old. With the increase in uptake of multigene panels, testing for genes outside of BRCA1 and BRCA2 has become more prevalent. This study looked at a single institution's cohort of women with multiple primary breast cancers that underwent panel testing to determine the rates of pathogenic mutations in non‐BRCA genes. The genetic testing results for each individual were reviewed, along with patient characteristics. Descriptive analysis and two‐tailed Z tests were used to analyze the data. Out of 85 eligible women, 33 (38.8%) tested positive for a pathogenic mutation in a cancer predisposition gene: 9 BRCA1, 5 BRCA2, 5 ATM, 1 BARD1, 4 CHEK2, 1 MSH2, 1 MSH6, 2 PALB2, 1 PMS2, 1 PTEN and 3 TP53. Overall, 17.6% tested positive for a non‐BRCA breast cancer predisposition gene. There was no difference in the age of first or second breast cancer diagnosis in comparison with genetic testing outcomes. This study found a high positive rate for all individuals with multiple breast cancers, regardless of age, for both BRCA1 and BRCA2 and non‐BRCA genes. Future studies should investigate whether individuals with multiple breast cancer primaries that do not meet BRCA1 and BRCA2 testing criteria should undergo genetic testing, regardless of the age of diagnosis.