A prostate-specific antigen, or PSA, level higher than 10 indicates up to a 67 percent chance of prostate cancer, according to WebMD. PSA levels between 4 and 10 indicate a 25 percent chance of prostate cancer; PSA levels under 4 indicate a 15 percent chance of the disease.
PSA is naturally produced by the prostate gland, explains WebMD. When prostate cancer is present, PSA levels tend to go up. However, elevated PSA levels can also indicate noncancerous conditions. For example, an enlarged prostate or prostatitis can cause elevated levels of PSA. A PSA blood test is the means by which most cases of early prostate cancer are found.