Approximately 195 patients will be included to receive subcutaneous trastuzumab a fixed dose of 600 mg every 3 weeks for 4 cycles (2 administered from the injection of a vial with a syringe and 2 with the injection device). Following administration of these four cycles, the patient will decide whether or not to continue with the subcutaneous formulation of trastuzumab every 3 weeks until progression. Since the randomization in the study until the start with subcutaneous trastuzumab, patients will receive a treatment cycle of intravenous trastuzumab as usual.