LAUSR

516Background: The MINDACT trial demonstrated that 46% of breast cancer patients (pts) at high clinical (C) but low genomic (G) risk based on MammaPrint (70-gene signature), might safely forego adjuvant CT (Cardoso NEJM 2016). A second 1:1 randomization (R-C) was optional in all pts for whom CT was decided, between standard anthracycline-based regimens (AT) and experimental docetaxel 75 mg/m² IV + oral capecitabine 825 mg/m² bid x 14 days (DC), q3wks for 6 cycles after surgery. Methods: MINDACT included 6693 pts, of whom 2895 received CT. C-low/G-low pts were allocated to no CT, C-high/G-high to CT and those with discordant G/C results were randomized to use either G or C risk to decide use of CT. Primary endpoint for R-C was disease-free survival (DFS). Secondary endpoints included OS and safety. Statistical hypothesis: HR-0.76 in favour of DC. Results: A total of 1301 pts (45%), of whom 787 (61%) were C-high/G-high, 351 (27%) C-high/G-low, 137 (11%) C-low/G-high, and 26 (2%) C-low/G-low, were randomized...