With your PSA of 4.4, let’s assume you have 100 prostate cancer cells. You want to destroy all of your prostate cancer cells. If you destroy all 100 prostate cancer cells there are none to make PSA so there would be no PSA made from your cancer. Although normal prostate cells make PSA, you also want to destroy all your normal prostate cells.
Remember, your cancer was started by one of your normal prostate cells transforming into a cancer cell. Whatever caused this change in your one cell could do it again in another normal cell in the future and then you would have a second prostate cancer. Because of this, you want to destroy not only all cancer cells, but all your normal prostate cells to keep you from getting a brand new prostate cancer. If you did this, then you would have no prostate cells, normal or cancer. Since only prostate cells make PSA and you would have neither normal nor cancer prostate cells, your PSA test would show this by going to zero.