Establishment and Validation of Extra-transitional Zone Prostate Specific Antigen Density (ETzD), a Novel Structure-based Parameter for Quantifying the Oncological Hazard of Prostates with Enlarged Stroma

Extra-transitional zone density (ETzD), a novel parameter is proposed to stratify the deviation of prostate specific antigen (PSA) due to structural change according to stromal hyperplasia of prostate. ETzD was conducted on a concept to estimate the PSA density (PSAD) after hypothetical enucleation of the transitional zone of an enlarged prostate by a non-linear regression prediction model with intrinsic linearity, from the retrospective analysis of PSA change observed actual enucleation by laser. The performance to predict the presence and severity of malignancy was validated by two cohorts of 3,440 prostate biopsies and 2,783 radical prostatectomy specimens. The performance of ETzD was compared with conventional parameters. The receiver operative curve of area under curve (AUC) of ETzD to predict the presence of malignacy was 0.862 (95% CI; 0.843~0.881), better than PSA, PSAD or transitional zone PSAD (TzPSAD). The AUC of ETzD to predict an unfavorable cancer among prostate cancer patients was 0.736 (95% CI; 0.705~0.768), which performs better than PSA and comparable to PSAD or TzPSAD. In summary, the performance of ETzD as a universal parameter to quantify the oncological hazard of a prostate was validated and the superiority to conventional parameters was verified.