My layperson's understanding is that the "normal" PSA baseline gets higher as men age. Also, 3.57 to 3.75 might be a normal variation from test to test (some of my other, non-PSA blood test results have been wildly different even from samples drawn on the same day and sent to different labs). I don't want to speculate further. Can you book a longer appointment to discuss with your radiation oncologist? If that's not possible, does your treatment centre have a patient-support line where you can talk with a trained oncology nurse?