[Diagnosis and follow-up of prostate cancer patients using prostate specific antigen (PSA)]

An international standard of prostate specific antigen (PSA) assays was constructed and prognosis of the patients with prostate cancers showing gray zone PSA was studied. For lower levels of serum PSA (< 50 ng/ml), the conversion formula to that of Tandem-R PSA from other assays was presented. Furthermore, based on the standards of Stanford Reference and Markit-MPA, conversion rates to this international standard from the conventional PSA assays were also obtained. Patients' cancer-specific survival was found to be significantly better in the gray zone group. Further studies to obtain higher specificity such as using free or complex rate in total PSA is necessary.