Study of Nivolumab Verses Nivolumab and Ipilimumab Combination in EGFR Mutant Non-small Cell Lung Cancer

This study examines the outcome of nivolumab single agent versus nivolumab-ipilimumab combination in patients with advanced EGFR+ NSCLC who have failed one line of standard EGFR Tyrosine Kinase Inhibitor (TKI) and not more than one line of chemotherapy regimen. The use of 3rd generation EGFR TKI for patients with acquired mutation that substitute a threonine (T) with a methionine (M) at position 790 of exon 20 (T790M) is allowed. Patients will be randomized in a 1:1 ratio to treatment with either nivolumab monotherapy (Arm A) or nivolumab/ipilimumab combination therapy (Arm B) and will be stratified according to the following factors: * Programmed Death-Ligand 1 (PDL1) status: \<1% vs ≥1% * Presence of brain metastasis * Institution: National Cancer Centre Singapore, National University Cancer Institute, and Johns Hopkins Singapore-Tan Tock Seng Hospital Both arms will continue with treatment regimen till disease progression or discontinuation of treatment due to adverse events. Arm A patients are allowed to cross over to Arm B in the event of clear-cut disease progression. On-study tumor assessments will be conducted every 6 weeks for 24 weeks and then every 12 weeks till clear-cut disease progression. The radiologist will be blinded to the treatment arm that the patient is randomised to ensure an objective response evaluation.