@rogo Was the ultrasound for an ongoing bladder situation like BPH?
Sometimes common issues like urinary retention, frequency, etc will obscure signs of PCa - especially with a low PSA.
You are quite lucky indeed that such a high grade cancer is still localized and can be successfully treated by either surgery or radiation.
Hopefully, genetic testing may reveal much about the inner workings if your particular disease and possible immunotherapies -and others- can be utilized to further combat it. Best,
Phil