Well, "had a treatment" is not proper English, so that's the first problem. A better comparison would be:
1: "A man who has run 20 miles is pretty close to being able to run a marathon."
2: "A man who ran 20 miles is pretty close to being able to run a marathon."
The first implies something about the man right now (he's the sort of guy who's run 20 miles, so he's probably able to run 26.2 miles). The second just says something about what the man has done in the past (he ran 20 miles), which doesn't imply the same sort of logical relation between what he's done in the past and what he can do now. The two are quite close, however.