I think different treatment centers use different levels of non detectable score. What my PCP said was it gets to a point where it is considered non detectable and I was told that number was .02.

PSA numbers when you have had a RP are worrisome as they (per my PCP) should be at the undectable level as you don't have a prostrate. Those who kept prostrate you will most likely have PSA levels that still go up and down based in irritations, activity, and hopefully not returning cancer. It is why the follow up PSA checks are so important.

I am not sure of definiton of cure. When you have cancer the possibilities of it recurring are much higher than an non cancer diagnosis. So my definition is what my oncologist/radiologist and PCP advises if should worry or not worry about a level or sign.

I don't believe you can use the term "cure" in reference to a specific PSA level. Cancer may still be lurking for years with an undetectable PSA, even ultra sensitive PSA. Different oncologists use different time frames to use the word "cure" in reference to various cancers. Five years, 10 ? Who really knows? In my medical career I have seen various cancers return after as much as a 20 year remission. With prostate cancer if it was high grade (Gleason 8-10) you are never off the hook.