If the patient can't tolerate the more aggressive treatment they may miss one or more of the chemos - bloodwork will determine if the chemo can be administered. Worse yet, it may interfer with the radiotherapy schedule: you really want to keep as close to that schedule as possible.

RE: bundled nodes - I've seen CT's showing bundled vs regular nodes somewhere online - not that I can tell the difference. It may be that the extent of the problem is only available with a neck dissection. I think you should ask again exactly what they meant about not knowing without the neck dissection.