I cannot speculate on what your ENT is thinking. Certainly it is correct that radiation's effects continue after treatment ends. He may consider doing surgery to remove what he considers a still active malignancy as a salvage (a terrible bit of medical phrasing, but what they call it) method. Your original post says that he had a left neck mass, so a unilateral dissection would seem appropriate. I can't say any more about the draiinage, like my previous post stated, it could be a sign of continuing maliganancy, or it could be drainage from the sluffing of tisssues related to treatment and even an infectious process combined with that. None of us here can really tell you more from our distant perspective and lay person's knowledge.