It's not because he knew better, but because he didn't like it. And frankly, who can blame him? The survival rate from pancreatic cancer is quite low, as is the median life expectancy. Moreover, he had the misfortune of getting a more aggressive variant. And the treatment is quite heavy.

Nevertheless, if it was me, everything considered, I'd still try to take my chances. And I believe most people would do the same. It's a pity, because there is still some chance he could still be around.