EPIDEMIOLOGY Survival with metastatic breast cancer based on initial presentation, de novo versus relapsed Wendie D. den Brok 1 • Caroline H. Speers 1 • Lovedeep Gondara 1 • Emily Baxter 1 • Scott K. Tyldesley 2 • Caroline A. Lohrisch 1 Received: 1 September 2016 / Accepted: 8 December 2016 Ó Springer Science+Business Media New York 2016 Abstract Purpose We hypothesized different Overall Survival (OS) in metastatic breast cancer (MBC) after relapse vs de novo presentation. Methods We identified women in British Columbia with MBC diagnosed between 01/2001 and 12/2009. OS from MBC was calculated for relapsed vs de novo cohorts in 3 subgroups, based on hormone receptors (HR) and HER2 status. Age at MBC, disease-free interval (DFI), de novo vs relapsed, year of MBC diagnosis, and systemic treatment were entered into univariable and multivariable analyses. Results We identified 3645 pts with known HR of which 2796 had known HER2. Median follow-up was 91 months. Median OS was longer for de novo vs relapsed MBC: HR?/HER2- 34 versus 23 months (mos) (p \ 0.0001), HR-/HER2- (TN) 11 versus 8 mos (p = 0.02), HER2? 29 versus 15 mos (p \ 0.0001). For TN disease, no variable independently discriminated a group with increased risk of death. For both the HR ?/HER2- and the HER2 ? groups, relapsed vs de novo status (HzR 1.4 [95% CI 1.2–1.5; p \ 0.0001], and HzR 1.6 [95% CI 1.4–1.9; p \ 0.0001], respectively) and age [ 50 (HzR 1.2 [95% CI 1.1–1.4; p = 0.001] and HzR 1.3 [95% CI 1.1–1.5; p = 0.01], respectively) were associated with increased risk of death on multivariable analysis. Conclusion These data provide information that may guide discussions about prognosis between physicians and patients with MBC. In addition, it highlights the impor- tance of stratifying for initial stage at diagnosis in future MBC therapeutic trials. Keywords Relapsed metastatic breast cancer Á De novo metastatic breast cancer Á Overall survival metastatic breast cancer Introduction Among the estimated 24,000 new cases of breast cancer diagnosed annually in Canada, about 5% will be stage IV or ‘‘de novo’’ metastatic at presentation. In addition, about 20–30% of incident stage I-III cancers will relapse with metastatic disease at some future time [1–5]. While median overall survival (mOS) for metastatic breast cancer (MBC) is described to be 2–3 years, we know it to be highly variable across individuals, due to both patient and disease factors. Given that prior adjuvant treatment may impact the behavior of cells in a metastatic focus due to clonal evo- lution and selective pressure [6–8], it is a reasonable hypothesis that de novo and relapsed MBC have different survivals. One retrospective study [9] reported better mOS for de novo disease, but did not examine survival by bio- marker subgroups. Retrospective studies of HER2? breast cancer in the trastuzumab era report conflicting results, some reporting better survival for de novo disease [10, 11] and others showing no difference [12]. Presented at (poster): SABCS (2014). Presented at (oral): CAMO (2015), Best of Oncology West (2015). Electronic supplementary material The online version of this article (doi:10.1007/s10549-016-4080-9) contains supplementary material, which is available to authorized users. & Wendie D. den Brok wdenbrok@bccancer.bc.ca 1 Department of Medical Oncology, BC Cancer Agency, 600 West 10th Avenue, Vancouver, BC V5Z 4E6, Canada 2 Department of Radiation Oncology, BC Cancer Agency, Vancouver, BC, Canada 123 Breast Cancer Res Treat DOI 10.1007/s10549-016-4080-9