My dad was successfully treated about
15 years ago. His PSA has never risen. But chances are, he won't be around at the 30 year mark, for reasons that have nothing to do with prostate cancer--he's already past the actuarial average lifespan of a man in the U.S. And he was younger than the average patient diagnosed with prostate cancer, which is still 70.
I am interested in this question, too, since I was diagnosed at 43. I'm especially interested in long term survival after salvage radiation, an area where followups are even shorter, because the technology hasn't been around that long. I'm watching the research of Andrew Stephenson and colleagues, in particular. They first released a multicenter study with a followup time of 4 years post-SRT, then updated it to 6 years. Catalona has released his single physician data on SRT patients looking out 10 years (and it's dismal compared to shorter term results).
It's important to realize that when you get very long time series, you are likely including men diagnosed before the advent of PSA testing, before advanced surgical techniques (like those developed by Walsh) were widespread, before 3D conformal radiation, protons, IMRT/IGRT, and before today's ADT drugs.
Nevertheless, there are a few studies that look back 20 or 30 years:
Dx Feb 2006, PSA 9 @age 43
RRP Apr 2006 - Gleason 3+4, T2c, NX MX, pos margins
PSA 5/06 <0.1, 8/06 0.2, 12/06 0.6, 1/07 0.7.
Salvage radiation (IMRT) Jan-Mar 2007
PSA 9/2007 and thereafter <0.1pcabefore50.blogspot.com