Why after prostate removed cancer all body scans neg lumps neg margins neg went for 6 weeks check up psa came back 2 upset need help?

Biochemical relapse: When only the PSA becomes elevated again without evidence by exam or scans that the cancer is back, doctors call this a biochemical recurrence. This generally means the scans used to detect cancer are still not sensitive enough to detect very small or microscopic prostate cancer cells that a lot of times are already in the bones but sometimes may still be in the previous prostate bed or nodes.