In an open-label , phase II , multicenter study , women with advanced breast cancer previously treated with 2 lines of chemotherapy for advanced disease , including both anthracyclines and taxanes , were randomized ( 1:1 ) to 3-hour infusions of trabectedin 1.3 mg/m ( 2 ) once every 3 weeks ( 1/3 treatment arm ) or 0.58 mg/m ( 2 ) every week for 3 of 4 weeks ( 3/4 treatment arm ) .