If you are in Group A, on Day 1 of Cycles 1-16, you will receive pembrolizumab by vein over 30 minutes. In addition, on Day 1 of Cycles 1-4, you will receive cisplatin by vein over about 2 hours and etoposide by vein over 4 hours on Days 1, 2, and 3. If you are unable to tolerate cisplatin, you will receive carboplatin by vein over 30 minutes and etoposide by vein over 4 hours on Days 1, 2, and 3.