ABSTRACT Purpose One year of H-based therapy, consisting of 18 q3w cycles, is standard of care for the adjuvant treatment of HER2-positive EBC. H is administered intravenously (IV) over 30–90 mins. An SC formulation of H has been developed, which is rapidly administered (up to 5 mins), potentially improving convenience for patients and clinical staff, and reducing administration costs. The Phase III HannaH study (NCT00950300) demonstrated that the pharmacokinetics and efficacy of H-SC were non-inferior to that of H-IV, meeting the co-primary endpoints. The safety profile of H-SC was comparable and consistent with the known safety profile of H-IV. SafeHer is designed to further evaluate the safety and tolerability of H-SC in a broader patient population; to allow greater understanding of a range of safety data. H-SC will be administered via one of two different routes (handheld syringe [vial formulation] or single-use injection device [SID]; which allows self-administration). Supportive data on SID safety and patient satisfaction with self-administration will be collected. Methods SafeHer is a multicentre, international, Phase III open-label trial (NCT01566721). The primary objective is the safety and tolerability of H-SC. Secondary objectives include disease-free survival, overall survival and patient satisfaction with SID administration. Immunogenicity of H and recombinant human hyaluronidase in a subset of patients using the SID at select sites is an exploratory objective. Planned enrolment is 2500 patients, assigned to one of two cohorts at the investigators' discretion ± concurrent/sequential chemotherapy. All patients will receive H-SC at a fixed dose of 600mg regardless of body weight, for a total of 18 cycles (q3w) via injection into the thigh over a period of up to 5 minutes. Patients in cohort A (n = 1800) will receive H-SC using handheld syringes. Patients in cohort B (n = 700) will receive H-SC using an SID, first via assisted administration and then self-administered (in select patients). Enrolment began in May 2012 and parallel substudies may be performed at selected centres to evaluate medical resource utilisation (“time and motion study”). Disclosure J. Gligorov: I disclose potential conflict of interest : advisory boards and speaker honoraria for Roche laboratories. H.A. Azim: I serve on the advisory board of Roche in the middle east. B. Ataseven: I am a Roche International Steering Committee member for the SafeHer trial. I have received speaker honoraria from Roche for giveing lectures. I participated in and received a travel grant from Roche for SABCS 2011. M. Delaurentiis: I am a member of a Roche Advisory Board. F. Herbst: I am an employee of, and am a stockholder in, F. Hoffmann-La Roche. A. Llombart: I am a member of a Roche Advisory Board. S. Osborne: I am an employee of Roche. X. Pivot: I am a member of Roche and GSK Advisory Boards. All other authors have declared no conflicts of interest.