Abstract PO4-14-03: Results of Comprehensive Genomic Profiling of Metastatic Breast Cancer Patients at a Single Institute in Japan

Abstract BACKGROUND. Comprehensive genomic profiling (CGP) was officially approved by the Japanese National Health Insurance System in June 2019. Currently, three CGP tests are available: FoundationOne CDx (F1CDx), OncoGuide NCC Oncopanel (NCC), and FoundationOne Liquid CDx (F1LCDx). This study examines the clinical significance of CGP testing in patients with metastatic breast cancer (mBC) in Japan. METHODS. The subjects were 105 patients (pts) who underwent CGP testing at our hospital from June 2019 to July 2023. Of these, 64 pts received tissue panels for F1CDx, 25 pts for F1LCDx, and 16 pts for others. Based on the reports from the testing companies and the expert panel committee's review, we evaluated the percentage of patients for whom matched therapy (MT) was recommended, whether MT was performed, and the prognosis of the group of patients for whom MT was performed. Overall survival was analyzed with the log-rank test. RESULTS. Of the 105 patients who underwent CGP testing, 47 pts (44.8%) were recommended MT corresponding to ESCAT(ESMO Scale for Clinical Actionability of molecular Targets) ranking I/II or clinical trials due to genetic alterations, and only 7 pts (6.7%) reached those treatments. Three HER2-negative patients were prescribed anti-HER2 therapy for ERBB2 amplification, one patient was prescribed entrectinib for NTRK fusion, and three patients participated in clinical trial for ERBB2 mutation and FGFR1 rearrangement. If ESCAT ranking beyond I/II and recommended therapy from FoundationOne report (e.g Abemaciclib for CCND1 amplification, Everolimus for PTEN loss)are added, 64 pts (60.1%) were considered these treatments, and 19 pts (18.1%) actually received these treatment. Among these 19 pts, overall survival was significant improved that of patientswho did not reach treatment (21.1 m vs 6.2 m, p=0.0097). CONCLUSIONS. We examined the rate of MT attainment by CGP in mBC at a single institute. We found that the rate of MT attainment with ESCAT ranking I/II, or clinical trials corresponding to genetic mutations, was low. The overall survival of patients who underwent MT, which can be performed by Japanese insurance, was significantly different from that of patients who did not undergo MT. Low accessibility of ESCAT ranking I/II MT may be because, in Japan, CGP testing is available only for patients who have completed or are expected to complete standard therapy. Early use of CGP testing and an increase in clinical trials will be desirable in Japan. Citation Format: Tomomi Kon, Hiroshi Tada, Minoru Miyashita, Akiko Ebata, Narumi Harada-Shoji, Yohei Hamanaka, Miku Sato, Mika Yanagaki, Satoko Tsunokake, Tokiwa Motonari, Asumi Yamazaki, Takanori Ishida. Results of Comprehensive Genomic Profiling of Metastatic Breast Cancer Patients at a Single Institute in Japan abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-14-03.