Anybody that thinks they are 100% cured after treatment is deluded. it can come back at any time. For me, I had a very small spot gleason 8 on the right side, had surger to remove the entire prostate and a lymph node sampling, everything came back from pathology as no spreading at all, no cancer in the sampled lymph, and 100% successful with a rapid drop in PSA to zero. It came back 9 months later. I am fighting it with hormone drugs that are starting to fail now.
Someone in my support troup had a recurrence after 10 years. That was rare but it happened.