I'm an HDR-BT guy so not identical to SBRT but SBRT was modeled after HDR-BT so in the same league at least. I just saw a slight rise from 0.7 8//2018 to 0.9 4/19 just over 36 months out. My next PSA is scheduled for August 2019.
Makes you a little nervous inside if you're anything like me, but as others have said, unless we see 3-4 consecutive PSA rises in a row and/or a total of 2.0 rise from nadir (currently 0.7 for me), not much to concern ourselves with at present. Hoping it's just a slight bounce of course. Let's keep on living with intention!