BRCA1 promoter methylation in breast cancer patients is associated with response to olaparib/eribulin combination therapy.
Kawachi Asuka,Yamashita Satoshi,Okochi-Takada Eriko,Hirakawa Akihiro,Tsuda Hitoshi,Shimomura Akihiko,Kojima Yuki,Yonemori Kan,Fujiwara Yasuhiro,Kinoshita Takayuki,Ushijima Toshikazu,Tamura Kenji
Breast cancer research and treatment
BACKGROUND:A PARP inhibitor is effective in breast cancer patients with BRCA1/2 germline mutations, and in cell lines with BRCA1 promoter methylation. However, its efficacy in breast cancer patients with BRCA1 promoter methylation is still unknown. METHODS:Biopsy samples were obtained from 32 triple-negative breast cancer (TNBC) patients treated with eribulin/olaparib combination therapy in a clinical trial (UMINID: 000009498) and analyzed for their mutations by FoundationOne CDx. DNA methylation was evaluated by quantitative methylation-specific PCR and bisulfite sequencing, and its level was adjusted for tumor cell fraction. RESULTS:Among 20 TNBC patients evaluable for both methylation and mutations, one (5%) and five (25%) patients had a high (> 80%) and low (30-80%) BRCA1 promoter methylation levels, respectively. One patient with a high methylation level, also having a BRCA2 mutation of unknown significance, displayed complete response. Among the 5 patients with low methylation levels, only one patient with a BRCA2 mutation of unknown significance displayed long-lasting disease control (24 weeks). Patients with a BRCA1 or BRCA2 mutation, or high BRCA1 promoter methylation showed better 6-month progression-free survival (PFS) compared with the other patients (P = 0.009). CONCLUSION:Quantitative methylation analysis suggested that addition of homozygous BRCA1 promoter methylation to mutations may more accurately identify TNBC patients who would benefit from olaparib/eribulin combination therapy. (209 words).
10.1007/s10549-020-05647-w