I don't know much about this type of cancer my dads died  of myeloma but I would say let him have the last word my dad was in denial too but you can't stop them living their life the way they want my dad died in 5 week after diagnosis he had one treatment and it made him worse he did not want anymore just be there for him that's the best you could do if I knew more about the cancer and that he did this I didn't know I would have been their for him more he was in and out hospital having blood transfusions and drip after drip in the end his organs failed although I was not allowed to see him if he can go home that's a great thing he will be around his family and friends instead of a hospital I soo wanted my dad to be with me but I did not have space in my house and it was not an option make sure his last things are in order even if he thinks he will live wills and so forth my dad did not leave a will because he kept saying he's fine till the end he said he was dying and it was too late sending love and hope