Phase II Trial of Continuation Therapy in Advanced NSCLC

OUTLINE: This is a multi-center study. Patients who have been treated with a PD-1 or PD-L1 inhibitor and experienced a PFS of ≥3 months will be enrolled within 6 weeks of last dose of PD-1 or PD-L1 inhibitor. On Day 1 of each 3-week cycle, subjects will first receive pembrolizumab at a dose of 200mg IV every three weeks in combination with chemotherapy. Partner chemotherapy will be either gemcitabine 1000mg/m2 IV D1 and D8 every three weeks, docetaxel 75mg/m2 IV D1 every three weeks, or pemetrexed 500mg/m2 IV D1 every 3 weeks (pemetrexed for non-squamous histologies only). Subjects will continue to receive this combination until progression or intolerable toxicity. Administration Sequence: First Sequence \- Pembrolizumab 200mg IV on Day 1 (cycle = 21 days) Administration Sequence: Second Sequence * Gemcitabine 1000mg/m\^2 IV on Days 1,8 (cycle = 21 days) * Docetaxel 75mg/\^2 IV on Days 1,8 (cycle = 21 days) * Pemetrexed 500mg/m\^2 IV on Day 1 (cycle -= 21 days)