Hormonal therapy causes most prostate cancer cells to undergo genetically programmed cell death (commit suicide) but never all of them. Some prostate cancer cells are resistant or can adapt to hormonal therapy and continue to survive. I recommend a PSA test every 6 months and a digital rectal examination once a year. If the PSA is in the undetectable range and the digital rectal examination reveals no lumps or bumps that seem suspicious for recurrent prostate cancer, no further testing is indicated. Although the vast majority of patients with recurrence of their cancer have a rising PSA, a few have a high-grade cancer that might not produce much PSA but might be detected on a digital rectal examination.