Participating investigators randomly assigned ( with an interactive voice response system ) patients 2:1 to receive an intravenous infusion of nivolumab 3 mg/kg every 2 weeks or ICC ( dacarbazine 1000 mg/m ( 2 ) every 3 weeks or paclitaxel 175 mg/m ( 2 ) combined with carboplatin area under the curve 6 every 3 weeks ) until progression or unacceptable toxic effects .