Nine hundred thirty-nine patients received induction therapy ( four 21-day cycles pemetrexed 500 mg/m and cisplatin 75 mg/m ) , after which 539 nonprogressing patients with an Eastern Cooperative Oncology Group performance status ( PS ) of 0/1 were randomized ( 2:1 ) to maintenance pemetrexed ( 500 mg/m ) cycles or placebo until disease progression .