I'll say that the general rule for most patients is to TAKE those meds! Me, I tolerate nausea better than the meds (actually allergic to some of them, we found out, yippee), but I've had YEARS of nausea practice prior to cancer, so that helped, weirdly. For anyone else, I'd advocate taking the stupid meds and keeping ahead of the misery ... and I'm not generally a big advocate of meds, despite what my bedside table might tell you.
I'd guess he's being stubborn / strong the way many men are when they get sick? but cancer offers plenty of bravery to go around, no need to suffer nausea too.