Would you consider using a PD-L1 inhibitor after progression on a PD-1 inhibitor for metastatic NSCLC?  

We do not have direct evidence to assess this question, but in the absence of data, I have been quite skeptical that switching from a PD-1 to a PD-L1 inhibitor would be an effective strategy. I think that the most direct data that I can offer from studies in which I have been involved is a study of ...