Abstract P1-14-02: Impact of loco-regional treatment (LRT) on overall-survival (OS) in patients with de novo metastatic breast cancer (MBC): Results of the French ESME multicenter national observational programme

Abstract

Abstract Background Previous retrospective studies and meta-analysis suggest an improved overall survival (OS) brought by loco-regional treatment (LRT) of primary tumor in de novo metastatic breast cancer (MBC) patients (pts), while prospective trials have mixed results. Most of the previous studies recruited pts before 2005 and consequently did not include recent medical therapies and advances used in MBC. Patients and methods The ESME database include individual data from MBC pts diagnosed between 2008 and 2014, who initiated their treatment in 1 of the 18 participating French comprehensive cancer centers. Our first aim was to study the impact of LRT, defined as surgery, radiotherapy or both, on OS in de novo MBC pts, defined as pts diagnosed with synchronous metastasis or within 90 days from diagnosis of primary tumor. OS was calculated from the date of diagnosis of metastatic stage and was estimated by the Kaplan Meier method. Univariate and multivariate analyses were performed using Logrank-test and Cox-model, respectively. Results Of the total ESME cohort (16703 pts), 4507 (26.9%) were diagnosed with de novo MBC and 4276 fulfilled inclusion criteria for the present study. Median age was 60 years. 66.3% pts had T3-T4. 13.1% (n=495) had triple-negative (TN) BC, 24.4% (n=918) HER2+ BC and 62.5% (n=2536) HR+/HER2- BC. Sites of metastases were bone (69%), liver (30.9%), nodes (29.5%) and lung (25.7%). 77.4% had less than 3 sites involved by metastatic disease. Of 4276 pts, 1706 (39.9%) received a LRT. Among them, 444 (26%) and 535 (31.4%) had surgery or radiotherapy alone respectively, 727 (42.6%) had a combination of both. 99% of pts received a systemic treatment: hormone therapy for 60.3% and chemotherapy +/- targeted therapy for 72.8% of them. Compared with pts with no LRT, pts in the LRT group were younger (median age: 57 vs 61 years, p<0.0001), had smaller tumor (40.4% ≤ T2 vs 28.2%, p<0.0001) with more N0 status (26.5% vs 19.3%, p<0.0001), and different phenotypes: TN 12.1% vs 13.8%; HER2+ 26.4% vs 23.1%; HR+/HER2- 61.5% vs 63.1% (p=0.0447). Metastatic disease in the LRT group was more likely to be limited to 1 or 2 sites (86.4% vs 71.4%), with more non-visceral sites (52.3% vs 36.5%). With a median follow-up of 45.3 m, median OS and initial PFS for the whole population were 45.2 m [95%CI: 43.3-47.1] and 13.8 m [95%CI: 13.2-14.4], respectively. Median OS for TN, HR+/HER2- and HER2+ pts were 19 m [95%CI:17-21], 47.4 m [95%CI: 45.2-50.4] and 53.3 m [95%CI: 48.9-60.2], respectively. By multivariate analysis, LRT was an independent prognostic factor for OS (HR=0.76; 95%CI: 0.64-0.89; p=0.001), together with age, histological subtype, number and patterns of metastatic sites. More advanced analyses will be presented in December. </del> Conclusion As in older series, this work finds that de novo MBC pts treated after 2008 may derive a prolonged OS, extending up to 4 years for HR+ and HER2+ subgroups. Given the classical prescription biases in such retrospective works, this should be carefully interpreted but might help in better selecting those pts for whom such strategy would be beneficial. Citation Format: Pons-Tostivint EEPT, Kirova YYK, Lusque AAL, Campone MMC, Levy CCL, Delaloge SSD, Mailliez AAM, Madrange NMD, Firmin NNF, Crouzet AAC, Gonçalves AAG, Jankowski CCJ, Lefeuvre CCL, De la Lande BBD, Puget NNP, Bachelot TTB, Ferrero J-MJMF, Uwer LLU, Eymard J-CJCE, Mouret-Reynier M-AMR, Petit TTP, Berchery DDB, Robain MMR, Filleron TTF, Cailliot CCC, Dalenc FFD. Impact of loco-regional treatment (LRT) on overall-survival (OS) in patients with de novo metastatic breast cancer (MBC): Results of the French ESME multicenter national observational programme [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-14-02.