"Gleason 6" never metastasizes." But Gleason 6 at one point sometimes later is Gleason 7=4+3 (4 is more prevalent than 3 in the biopsy.) And Gleason 7=4+3 can actually be 4+3+5 (the score is the two most prevalent types of cells in each biopsy.) And when my prostate was removed, there was one small spot with negative margins (the cancer[-ish, if you feel like Cooperberg] cells extended to the edge of what was reviewed by the pathologist after the surgery. And yes, in that case, there is a 50-75% likelihood the cancerous "prostatic" cells prosper to the point of being identifiable outside the prostate itself. (Metastasis is defined as secondary malignant growths at a distance from the primary site, not adjacent to it.)
So yes, I can agree that Gleason 6 "never" metastasizes--by definition. So if you want to call it something other than cancer, that's fine with me.
I began "active surveillance" in my early 40s. However, 20 years and some major relocations later, that surveillance was not only less active, it became inactive. (I didn't know the standard medical screening guidelines had changed and my then primary MD did not know or discuss my relevant history, she just didn't order the screening with my bloodwork.) When that changed and I had a better MD, behold, a lot more PSA for my somewhat enlarged gland and with an mpMRI, behold, a nodule of concern. But then the next mpMRI, behold, a second nodule of greater concern (2 months apart, so probably a difference in data and/or interpretation, not growth.) And then the mpMRI guided transperineal biopsy, behold, intermediate unfavorable (7=4+3), only in the nodule not discovered on the first mpMRI.
So that is my story of how I went from "this is overblown" to Stage 2 (where Stage 4 is metastasis.) Of course, I would still like to stop where I am, but my active surveillance post-RALP is a lot more active now than it was a few years ago :-).