How Can Neck Cancer Be Treated?

My dad found out he had stomach cancer almost years ago, stage 4. He underwent immunotherapy and saw great improvement. Cancer receded from his brain and blood from what i was told. He now just found out there is cancer in his neck affecting the nerves. No loss of bladder or bowl control, no loss of limb function, only shaking hands and neck pain. He says to me that it is nothing to worry about and that if the doctor says something bad about it he will tell me. Can I trust this? In my opinion any spread of cancer is bad especially with him being diagnosed at stage 4. Can you help me?