Just to be clear, in my mind "active surveillance" is not "watchful waiting." Getting an mpMRI is totally compatible with active surveillance. And, of course, acting on the results of surveillance is totally compatible with a period of active surveillance. 🙂
Since prostate cancer generally is not first recognized by directly observable physical symptoms, a case can be made that almost every PC journey begins with active surveillance, so really the question is when to move from passive indifference to active surveillance, and when to move from active surveillance to some sort of intervention. I suppose even a biopsy could be viewed as active surveillance--perhaps hyperactive?!
This really threw me a bit when I got a higher PSA reading than previously. My primary care MD said he could either refer me to a urologist or order an mpMRI. I thought, well, the first thing a urologist is going to do is order an MRI, so I might as well go ahead. It turned out that was cutting edge medicine as far as my insurance company was concerned, but of course it makes a lot of sense, as the MRI is about the cost of two urologist appointments :-). It also helped me realize I didn't want a third party technician with a (out of date?!) manual second guessing my medical care.
Unfortunately (or fortunately), the results accelerated my journey to treatment. I actually first saw the urologist who did my RALP after a transperineal biopsy at a center of excellence and less than a month before the RALP.