Most of the data points mentioned in that UroToday paper somehow track back in some way to looking at mortality (between patients managed with active monitoring versus radical treatment).

Beyond looking at mortality, quality of life is of great importance. For just a Gleason 6, radical treatment can often be worse than the possible cancer itself.

In the early 2000s, so many men were opting for radical treatment for a G6 (usually surgery) when it wasn’t medically necessary, that in 2012 the United States Preventive Services Task Force (USPSTF) recommended against routine prostate cancer screening (assigning the screening a “D” recommendation: https://www.uspreventiveservicestaskforce.org/uspstf/recommendation/prostate-cancer-screening-2012).

As it turned out, that knee-jerk reaction had bad downstream consequences. But, it was as a result of so many unnecessary radical treatments for G6 and the adverse quality of life impacts they caused.