Optimal duration of adjuvant chemotherapy for high-risk node-negative (N–) breast cancer patients: 6-year results of the prospective randomised multicentre phase III UNICANCER-PACS 05 trial (UCBG-0106)

•1516 high-risk breast cancer patients were randomised in 58 investigation centres.•DFS rate at 5° years was 88.4% (4 FEC 100) versus 92.1% (6 FEC 100), HR = 1.18, P = .24.•Grade 3 and 4 neutropenia were significantly more frequent with 6 FEC 100.•The results suggest a trend toward better DFS and OS in the 6 FEC 100 arm.•Assessment of high-risk patients must be more accurately defined.