Some begin testing, such as a biopsy, even sooner, at 2.5 nanograms per milliliter (ng/mL).In the study, the 71 men with advanced cancer all had prostate specific antigen (PSA) levels above 100 ng/mL. The median PSA in the men was nearly 400.None of the 71 men -- whose average age was 67 -- had been tested for PSA before at the Santa Clara hospital, and Reese said he suspects most or all had never