He does say this. After punching the dude in the diner, he makes a joke about "will I ever play the violin again?", but of course he doesn't play the violin at all. The follow up is something along the lines of "but what about my promising career as a neurosurgeon?" They all of course treat it as a joke too.
Personally, I think he was only half joking. Later on at the hospital, Maddie refers to him as "Doctor" twice and makes the comment of it being "good to meet" him. That could mean nothing and she was just being polite, but seemed potentially intentional. So my speculation is that he is/was a neurosurgeon of some renown, which makes it just extra sucky to end up with an inoperable brain tumor.
If I recall correctly, in that scene, I think either he or the female doctor makes mention of a "treatment" that he is taking, but they don't go into details. I suspect, assuming there is a "he doesn't die" ending for the game at all, it will probably be some kind of experimental treatment, with a very slim prognosis for improvement, but he's trying it anyway. And then either it's going to work, and he will be cured, or perhaps one of his old colleagues will develop a new treatment based on his work (and the current trial treatment), OR, they will find out that they can actually do surgery, because of some new breakthrough procedure, that is less invasive, or requires no surgery directly (like lasers to burn the tumor or whatever). I suspect it will probably have like a "but the treatment can only happen in Bumfukiztan, forcing the MC to say goodbye and leave "forever". And then the ladies will save up and come stay with him or something, to give us the surprise happy ending with his hooker harem. That's the general way I see the Happy Ending going for this story, again, assuming it has one at all.