How long would it take untreated oral cancer to kill a person?

well my husband has oral cancer it was stage 4 he was in so much pain he was on morphine,percet,hydro,pain patch,morphine pump.they did the surgery in august and removed the very large tumor tongue ,floor of mouth ,jaw bone ,lympnodes in his neck this is called a radical neck dissection with a flap and a titanium plate to hold the bone graft together with out the surgery they said he could live 2 years but the pain would be to great for him to stand it hope this has helped you n your decesion the surgery took 14 hours he was hope in 8 days he can talk ,eat some things with his mouth the only pain we have now is from the plate which is going to have to come out soon good luck