Abstract P5-12-02: Germline variants detected by next-generation sequencing-based multigene panel testing in patients with suspected hereditary breast cancer at a University Hospital in Japan

Background: The usefulness of prophylactic surgery and surveillance for hereditary breast cancer has been demonstrated, and germline testing for BRCA1 and BRCA2 had been covered by insurance since 2020 in Japan. In addition to BRCA1 and BRCA2, several other genes are also associated with an increased risk of developing breast cancer, such as PALB2, ATM, BARD1, CHEK2, PTEN, and TP53. Next-generation sequencing-enabled multigene panel tensing provides information about these gene variants at the same time, and at a low cost. Although germline testing of BRCA1 and BRCA2 has become widespread in Japan, multi-panel gene testing for germline variants has been conducted only in a limited number of facilities, partly due to the difficulty associated with dealing with the gene variant information obtained from the test. The aim of this study was to clarify the current status of multigene panel testing in our institute, and reveal the characteristics of the variants detected in patients with, or predisposed to, hereditary breast cancer. Methods: This retrospective study included 37 individuals who underwent next-generation sequencing-based multigene panel testing in order to investigate any inherited genetic variants due to a suspicion of hereditary breast cancer. Eighteen patients had a diagnosis of breast cancer with a family history of breast and/or ovarian cancer, nine patients had a diagnosis of breast cancer without family history of breast or ovarian cancer, and 10 patients had a family history of breast cancer but had not developed breast cancer themselves. Results: Utilizing mutigene panel testing, at least one alteration was found in 24 genes, and a total of 39 variants were found in the 37 patients. Of these 37 patients, nine (24.3%) had a pathogenic/likely pathogenic variant with or without other variants of uncertain significance (VUS), 15 (40.5%) had VUS, and 13 (35.1%) had negative genetic test results. Among the nine patients with pathogenic/likely pathogenic variants, seven had variants in either BRCA1 or BRCA2 (one BRCA1 pathogenic variant, five BRCA2 pathogenic variants, and one BRCA2 likely pathogenic variant), while the remaining positive results were attributed to other genes (one MLH1 pathogenic variant, and one SDHB pathogenic variant). VUS included BRCA1 and BRCA2, as well as other breast cancer-associated genes, such as ATM (n=2), CDH1 (n=2), NF1 (n=2), PALB2 (n=1), CHEK2 (n=1), NBN (n=1), and RAD51D (n=1). VUS also included other cancer syndrome-related genes, such as MLH1 (n=2), MUTYH (n=2), APC (n=1), and RET (n=1). Conclusion: Multigene panel tests in our institute revealed pathogenic/likely pathogenic variants in 24.3% of individuals who suspected hereditary breast cancer. As expected, multigene panel tests also revealed more VUS than pathogenic variants and 40.5% individuals were detected with VUS, which included many genes associated with hereditary breast cancer and other cancer syndromes, in addition to BRCA1 and BRCA2. Individuals with VUS will need to cope with new information if the interpretation of the variant changes in the future. We need to be aware of the characteristics and limitations of this type of panel testing, and to properly utilize the test results and information obtained for good quality patient care. Citation Format: Yusa Atake, Masayuki Nagahashi, Haruka Kanaoka, Akira Hattori, Ayako Bun, Reiko Fukui, Hiromi Ozawa, Yukie Fujimoto, Tomoko Higuchi, Michiko Imamura, Keiko Murase, Yuichi Takatsuka, Mina Kashima, Chiho Okada, Chinatsu Kinjo, Mikako Miyata, Ayako Miyazaki, Mako Ueda, Hiroshi Tsubamoto, Hideaki Sawai, Yasuo Miyoshi. Germline variants detected by next-generation sequencing-based multigene panel testing in patients with suspected hereditary breast cancer at a University Hospital in Japan [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-12-02.