It really depends on the specific type of cancer more than the stage how well it responds to treatment. I know someone who had stage 4 lymphoma, and I believe non Hodgkins. He's been in remission for 3 years.
Also doesn't NHL have a pretty high survival rate. I mean the majority of people who get it seem to be diagnosed at Stage 3 and it still have something like a 70% survival rate.
It's not like he has parcratic or lung cancer both of which seem to be have 95%+ mortality rates.
Prayers for Governor Hogan and his family too!