Prevalence and clinical significance of germline pathogenic variants identified by multigene panel testing in high-risk Japanese patients with breast cancer.

In Japan, BRCA genetic testing for the diagnosis of hereditary breast and ovarian cancer is covered by medical insurance. However, other breast cancer (BC) susceptibility genes are rarely examined in these patients, primarily because medical insurance does not cover testing for these genes. A multigene panel testing (MGPT) was conducted on patients with BC who met the clinical criteria for BRCA genetic testing. Of the 494 patients, 45 germline pathogenic variants (GPVs) were identified (9.11%). The BRCA genetic testing criteria items with GPV detection rates > 10% were as follows: "diagnosed at age ≤ 45 years," "diagnosed with triple-negative breast cancer (TNBC) at age ≤ 60 years" and "≥1 close blood relative within the third degree on the same side of the family with breast, ovarian, or pancreas cancer." . MGPT can identify GPVs in genetically high-risk BC patients, including both BRCA1/2 and non-BRCA genes. Thus, MGPT may be an effective approach to support appropriate clinical management for both patients and their relatives.