My brother in law has stage 4 cancer spread from nose to throat and neck, but not any futher has had chemo and radiotherpy ( 6 weeks), if cured what chances of coming back, at this is stage what percentage does cure it if any?

Need more info: Even with stage 4 head and neck cancers, some patient do survive. Survival depends in part on the site of origin. For nasopharynx cancers, the seer data (from the national cancer institute) show 37% of patients still alive 10 years after diagnosis. Other sites of origin are better, or worse, than that number. These data are for patients diagnosed between 1988 and 2001. 2012 data may be better.