Chances are the clean nodes indicated no further treatment needed - this always concerns me but treatment is so brutal that they only like to give it if it meets the parameters layed down by the national cancer center. usually this is at the very minimum nodal involvement or peri neural involvement. It's rare that this cancer skips the nodes and moves elsewhere but it does happen. Your drs. Did the right thing with the neck dissection - how big was his tumor? Hugs.