I do wonder if a 5 year whole body MRI or CT would be generally beneficial for the population. I don't think it needs to be Annual to have benefits.
The problem is it really isn't uncommon for your body to create random puss fill sacks all over the place. It's one thing our cancer doctor warned us about. My wife is now on a 6 month CT regimen and ultimately, they'll just ignore new lumps.
GP wasn't asking what they should personally do. They were asking how the doctor would screen for it. (The truth is, the doctor can't/won't-- an annual MRI on every otherwise healthy person, for example, would be prohibitively expensive with how MRIs are currently set up-- and as another commenter pointed out, findings from those can be just as easily ignored or put off until it's too late.)
Being beside that hypochondric point is statistically a much healthier place to be.
The current state of medicine is the current state of medicine in the actual world.
Annual MRI?