Intravenous administration has been the standard formulation to deliver trastuzumab in HER2-positive breast cancer patients. The essential concerns with intravenous delivery are that a patent intravenous line is required and the infusion time. A new potential subcutaneous delivery method for trastuzumab has been recently developed, which is rapidly administered, potentially improving convenience for patients and clinical staff, enhancing medical resources, and reducing administration costs. In the neo/adjuvant setting, the phase III HannaH study showed the non-inferiority of subcutaneous trastuzumab when compared with the intravenous formulation. Based on comparable pharmacokinetics, efficacy, and safety, the subcutaneous formulation and regimen provide an alternative treatment to the registered intravenous formulation for stage I to IIIC HER2-positive breast cancer. The safety profile of subcutaneous trastuzumab was comparable and consistent with the known safety profile of trastuzumab. The phase III SafeHer study will further evaluate the safety and tolerability of subcutaneous trastuzumab in a broader HER2-positive breast cancer patient population. In addition, the study called PrefHer showed that patients preferred fixed-dose subcutaneous delivery of trastuzumab via a single-use injection device over standard intravenous administration for the treatment of HER2-positive early breast cancer. In conclusion, patient efficacy, safety, and preference suggest that a fixed dose of 600 mg subcutaneous trastuzumab every three weeks is a validated, well tolerated, and preferred option of patients for the treatment of HER2-positive breast cancer. [ABSTRACT FROM AUTHOR]