Is there a maximum period of elapsed time after which you would no longer consider radiation to a positive margin following surgery for NSCLC?  

There's a lot to consider in a situation like this. All the available data (to me at least) suggest the role of PORT is local/regional control. In the advent of good chemotherapy, the role in a true adjuvant setting is pretty small/none. What you're describing is this rare gray zone of positive marg...