CASE PRESENTATION: 65-year-old male with COPD(not on home oxygen O2) & stage IIA NSCLC underwent chemo-radiation therapy with remission for 2 years. During PET/CT surveillance, bilateral hilar FDG-avid masses were noted & sub-carinal lymph node fine needle aspiration was consistent with atypical cells suspicious for reoccurrence. Nivolumab was started. After 5 cycles of Nivolumab patient developed hypoxia(SaO2 72% on room air) with diffuse ground glass infiltrates & consolidative changes. Prednisone taper over 6-weeks was initiated & he was discharged home on 2L O2. Nivolumab was restarted after 4 weeks. Patient again presented with profound hypoxia(SaO2 60% on room air), requiring 4L O2, had right pleural effusion, required draining & repeat course of prednisone. Introducing Nivolumab 3rd time was thought to be detrimental & patient was offered gemcitabine instead, for recurrence.