Abstract P2-19-01: Impact of bone-only metastatic breast cancer on outcome in a real-life setting: A comprehensive analysis of 5,041 women from the ESME database

Background: Bone-only (BO) metastatic breast cancer (MBC), defined as bone as unique site of metastasis at MBC diagnosis, is thought to carry a better prognosis among MBC. However, only small retrospective series and data from selected randomized controlled trials have been reported so far. Based on a national database, we aimed at providing a large comprehensive analysis of BO MBC, and at evaluating its impact on clinical outcome. Methods: The ESME MBC platform (NCT03275311) is a French multicenter retrospective real-life database using a clinical trial-like methodology to collect data from 18 French Comprehensive Cancer Centers. It includes data from each newly diagnosed MBC patient having initiated at least one treatment between 2008 and 2016. BO cases occurring in women were retrieved and compared to the overall non-BO population, regarding treatment effects and survival. Results: Of the 22,463 women selected in the database, 5,041 (22.4%) patients with BO disease were identified. Most (N=4,102, 81.4%) had HR+/HER2- disease while 644 (12.8%) and 295 (5.9%) patients had HER2+ or HR-/HER2- disease, respectively. Compared to non-BO MBC, BO MBC patients were older in the global cohort and in HR-/HER2- patients (mean age 61.0y versus 59.5y, and 59.3y vs 56.4y, all p Conclusion: This large comprehensive study is the largest cohort of BO MBC to date. BO MBC has a distinct presentation from non-BO MBC and carry a better prognosis compared to non-BO MBC. A significant proportion of BO MBC patients have a very long survival and may benefit from aggressive local therapy, as stereotactic radiotherapy. Dedicated studies are warranted to tailor the management of these patients. Funding: This work was supported by UNICANCER. The ESME MBC database is supported by an industrial consortium (Roche, Pfizer, AstraZeneca, MSD, Eisai and Daiichi Sankyo). Data collection, analyses and publications are totally managed by RD 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P2-19-01.