I certainly would not cancel any scheduled followup appointments. If something (forbid) were to happen later, the doc could wash his hands of you.
I have the same PSA issue with my uro. Even though the lab and the test are the same, he specifies the less-sensitive report, so from him I only get from <.1 and up. I had to get my GP to run ultra-sensitives before I broke .1.
I'm not so sure that the uro is wrong in not doing the ultra-sensitive. Too much knowledge may not be a good thing. Now that I am above .4, it doesn't matter anymore.
Anyway, back to the good news, by the standard of being "undetectable", you will be a welcome member of the Zero Club. Sorry I'm not there these days, guess I'll offer myself a round tonight