Why Would PSA Still Rise after a Prostatectomy?

Dear Dr. Motola,

My prostate has been surgically removed and radiation was given out of concern for a slowly rising PSA. After this was done, we went back to the doctor to find out the results and learned that my PSA was still rising slowly. Is there an explanation for this? I thought PSA could only apply to someone with a prostate. Please help me understand this.

If the PSA continues to rise after a patient undergoes surgery and radiation for the treatment of prostate cancer, this implies that there is a recurrence of the cancer, either locally in the region of the previous prostate, in nearby lymph nodes, in bone, or circulating tumor cells. Depending on the rate of the rise of the PSA, your age, and characteristics of the original tumor, further treatment may be indicated.