Low psa does it mean no cancer

I'm betting you meant <0.1.
No, it doesn't mean no cancer. But it does mean undetectable, which isn't the same.
Are you on any sort of ADT like Lupron?
Without ANY further treatment if your PSA stays the same, in about two years you could claim remission. Cure is more like 5 years.

Would you post your diagnosis and any treatment you've had in your profile. We could get a better idea where you are at.

You had radiation therapy. Hence, a PSA that low (<0.1) is fine!
Hope it stays that low for a long time.