- Completed single-agent trastuzumab emtansine or combination trastuzumab emtansine treatment in the parent study or who continue to receive single-agent trastuzumab emtansine or combination trastuzumab emtansine treatment at the time of the parent study closure and received the last study drug dose within the 6 weeks (42 days) prior to the first dose of study therapy on the extension study or Continue to receive treatment in the control arm of study BO21976/TDM4450g (NCT00679341) at the time of the parent study closure if the participant received the last dose of control arm study drug within the 6 weeks (42 days) prior to the first dose of control arm study therapy in the extension study