Nine-Week Versus One-Year Trastuzumab for Early Human Epidermal Growth Factor Receptor 2–Positive Breast Cancer: 10-Year Update of the ShortHER Phase III Randomized Trial

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned coprimary or secondary analyses are not yet available. Clinical trial updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported. We present the final analysis of the phase III noninferiority, randomized ShortHER trial comparing 9 weeks versus 1 year of adjuvant trastuzumab with chemotherapy in patients with human epidermal growth factor receptor 2–positive (HER2+) early breast cancer (BC). Women with HER2+ BC were randomly assigned to anthracycline-taxane combinations plus 1-year trastuzumab (arm A, long) or 9-week trastuzumab (arm B, short). Here, we report the second coprimary end point overall survival (OS), updated disease-free survival (DFS), and outcomes according to hormone receptor status, age, and nodal status. At a median follow-up of 9 years, 10-year DFS is 77% versus 78% in the long versus short arm, respectively. Ten-year OS is 89% versus 88% in the long versus short arm, respectively. 10-year DFS rates in the long versus short arm according to nodal status are N0 81% versus 85%; N1-3 77% versus 79%; and N4+ 63% versus 53%. Ten-year OS rates in long versus short arm according to nodal status are N0 89% versus 95%%; N1-3 92% versus 89%; and N4+ 84% versus 64%. The updated analysis of the ShortHER trial shows that 1-year trastuzumab is the standard treatment for patients with HER2+ early BC as noninferiority cannot be claimed. However, numerically, the differences for the patients at low or intermediate risk (N0/N1-3) is negligible, while patients with N4+ have a clear benefit with 1-year trastuzumab.