I Had Prostate Cancer, Last Psa Is Seventy Four. I

I had prostate cancer,
Last psa is seventy four. I have had a rad prostatectomy a year ago. Ct and bone scans are negative. The doc wants me to start lupron based on the high psa levels. I am concerned about side effects,and the usefulness of the drug. Since my surgery the psa has been fluctuating ,which causes me to wonder how reliable or how thorough the tests are. Are there any other tests that can be done, that are more accurate to determine where there is mets. Are there others factors that can cause elevated psa