The patient is receiving a combination of radiotherapy and chemotherapy. The surgery to remove the cancerous throat tissue was not entirely successful as the surgeon discovered that the cancer had metastasised to the lower pallet. The patient is male, in his early 60s, very athletic and fit, in excellent health with great cardiovascular capacity, etc.
Roughly speaking, it appears that about 30-40% of patients in stage IV will survive for 5 years or more depending on where the cancer originated. This reference provides details.
There is a large difference in survival depending on whether the cancer was caused by HPV or ( probably) tobacco/alcohol. The HPV cancers have significantly higher survival rates. I am surprised the ACS information does not point out this difference. I was diagnosed with oral cancer about 9 years ago ( age 74), I had likely had it for a couple years before that, as initially 6 doctors missed the symptoms.Stage IV, chemo,radiation,surgery ( Oct '13) . MDAnderson quickly diagnosed HPV as the cause.