OP are you worried your doctor will refuse treatment for other things?
I have a small window into that worry. Every doctor is different. My mum has refused many "life saving treatments" for 10+ years now. She did worry that other things would go untreated but it's been okay. If she has a fall, she's still entitled to be checked out for broken bones etc.
She also organised a DNR for herself and was met with clear disapproval but you just have to say "fuck em" in your head.
On my end, I had a cancer scare and it turned out to be nothing (after several invasive tests and I refused a needle biopsy) but the GP got as far as telling me I should prepare for looking at treatment options and inform my family!
I wanted palliative only, I was 42 at the time and that was enough for me. I called my best friend and told her I loved her but I would not have cancer treatment.
Now I'm 47 and still feel the same.
I have no doubt they'd question me heavily but the short version is, when it's my time, I'm off.
I have also seen what cancer treatment did to my dad and I wouldn't see the point in extending life for that.
I think you have to gird yourself for doctors trying to "persuade" you, as they have my mum.
But if you are worried you won't treated for, say, an ear infection, because you refused cancer treatment, I don't think you need to worry about that.