Abstract P2-15-12: Effect of Bevacizumab and Eribulin for metastatic breast cancer in the real world evaluated using the propensity score matching analysis (PSMA) and inverse probability of treatment weighting analysis (IPTWA)

Background: Bevacizumab (BEV) + Paclitaxel (PTX) and Eribulin represent the most frequently agents for the treatment of HER2-negative metastatic breast cancer (MBC). Eribulin has improved overall survival (OS) in EMBRACE trials. On the other hand, BEV has improved progression free survival (PFS) in several clinical studies, but not revealed prolongation of OS in them. There are difficult situations in making a clinical decision of when to choose which treatment option.Purpose: The purpose of this study is to compare two treatment strategies, Eribulin followed by BEV + PTX versus BEV + PTX followed by Eribulin. We evaluated whether sequential order of treatment affects survival benefit in patients who have been treated with both BEV + PTX and Eribulin in the real world. Methods: All patients who started BEV + PTX and Eribulin treatment for MBC from Aug-2011 to Jun-2018 were selected. Among 264 patients recorded in the TBCRG (14 institutions of Research Group) database, 180 patients had HER2-negative MBC. Of these, 84 patients were treated with both BEV + PTX and Eribulin sequentially regardless of treatment line. To evaluate the influence of sequential order, we compared the efficacy of Eribulin followed by BEV + PTX (arm E-B) to treatment with the reverse sequence (arm B-E). We used the two different analytical approaches to rubstify the findings from this study. Results: 38 patients were treated with E-B and 46 patients with the B-E sequence. We analyzed 60 cases within 3rd-line. In the entire cohort, the median time to failure of strategy (TFS) was 9.9 and 16.8 months in arm E-B and arm B-E, respectively (HR = 0.503, 95%CI 0.298-0.889, p=0.017). The respective median OS was 17.2 and 28.0 months (HR = 0.663, 95%CI 0.349-1.261. p=0.21). Similar HRs were derived from the PSMA and IPTWA cohort in TFS. Using PSMA, TFS was 9.0 and 14.1 months in arm E-B and arm B-E, respectively (HR = 0.406, 95%CI 0.172-0.955, p=0.039). The respective median OS was 12.8 and 24.0 months (HR = 0.61, 95%CI 0.232-1.6, p=0.315). Using IPTWA, TFS was 10.2 and 14.8 months in arm E-B and arm B-E, respectively (HR = 0.621, 95%CI 0.423-0.913, p=0.015). The respective median OS was 17.5 and 24.0 months (HR = 0.86, 95%CI 0.547-1.352, p=0.513).Conclusion: These results suggest that when patients with HER2-negative MBC are treated with both BEV + PTX and Eribulin, patients with prior BEV + PTX treatment is more likely to show more significant difference in results benefit than patients who are treated with prior Eribulin treatment. Citation Format: Koshi Matsui, Mitsuharu Earashi, Takuya Nagata, Akemi Yoshikawa, Wataru Fukushima, Zensei Nozaki, Yasuko Tanada, Kaeko Oyama, Katsuo Shimada, Kaoru Kiyohara, Tetsuro Shimizu, Keiko Iwata, Toru Yoshida, Kiichi Maeda, Akiyoshi Nakakura, Satoshi Morita, Tsutomu Fujii. Effect of Bevacizumab and Eribulin for metastatic breast cancer in the real world evaluated using the propensity score matching analysis (PSMA) and inverse probability of treatment weighting analysis (IPTWA) [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P2-15-12.