The PERSEPHONE trial: Duration of trastuzumab with chemotherapy in women with HER2-positive early breast cancer.

TPS660 Background: Persephone is a phase III randomised controlled trial comparing six months of trastuzumab to the standard 12 month duration in patients with HER2 positive early breast cancer in respect of disease free survival, safety and cost-effectiveness. A Persephone sister study, the PHARE trial run by the National Institute for Cancer, successfully closed to recruitment in 2010. A prospective meta-analysis is planned once each trial has reported individually. Methods: A total of 4000 patients will be randomised into each of the two treatment groups. The power calculations assume that the disease-free survival (DFS) of the standard treatment of 12 months trastuzumab will be 80% at 4 years. On this basis, with 5% 1-sided significance and 85% power, a trial randomising 2000 in each arm will have the ability to prove non-inferiority of the experimental arm defining non-inferiority as ‘no worse than 3%’ below the control arm 4 year DFS. Primary outcome is disease-free survival non-inferiority (equival...