Assessment of Prostate Volume and Prostate-specific Antigen Density With the Segmentation Method on Magnetic Resonance Imaging

Abstract

Background/Aim: This study aimed to compare the prostate volume (PV) and prostate-specific antigen density (PSAD) obtained using the ellipsoid volume formula or segmentation methods on magnetic resonance imaging (MRI) and further predict prostate cancer (PCa). Patients and Methods: Retrospectively, the enrolled patients underwent prostate MRI and had PSA levels between 4 and 10 ng/ml. The PV was measured with both the ellipsoid volume formula (PVe) and the segmentation method (PVs). The transitional zone volume (TZV) was measured with the segmentation method. The PSADe, PSADs, and PSAD_TZV were calculated. Bland-Altman plots were used to compare the agreements. ROC curve analysis was used to compare the diagnostic accuracies to predict PCa. The results were also compared between the PCa and the no-PCa groups, and among tumors with different locations and different Gleason scores (GS). Results: Seventy-six of the 117 enrolled patients were classified into the PCa group. There were high agreements between PVs and PVe as well as between PSADs and PSADe, while several outliers were mainly due to posttransurethral resection of the prostate changes and irregular hyperplastic nodules. The diagnostic accuracy of PSADe (AUC: 0.732) was slightly higher than that of PSADs (AUC: 0.729) and PSAD_TZV (AUC: 0.715). The PSADe and PSADs were not different among different tumor locations but were higher in GS ≥7 lesions (both p=0.006). Conclusion: The segmentation method can be an alternative method to measure PV and calculate PSAD before prostate biopsy, particularly in post-transurethral resection of the prostate patients or those with irregular hyperplastic nodules.Prostate cancer (PCa) is the second most common cancer in men worldwide, with approximately 1,414,259 cases (7.3% of all newly diagnosed cancers) in 2020. Its incidence is especially higher in countries with a higher human development index (HDI) than in countries with a lower HDI (37.5 per 100,000 males vs. 11.3 per 100,000 males). The incidence rate has continuously increased in some countries or regions, such as China, Eastern Europe, and sub-Saharan Africa (1).In Taiwan, the incidence rate of PCa is exploding. Between 2009 and 2019, the incidence rate increased from 34.49 to 60.70 per 100,000 males. Meanwhile, the mortality rate of PCa also increased from 8.04 to 13.14 per 100,000 males (2). The main reason for the increasing incidence rate is the use of screening tools, including a combination of prostate-specific antigen (PSA) screens using a cutoff threshold of 4 ng/ml and digital rectal examination (DRE). However, there are some limitations to PSA and DRE. The positive predictive values of PSA and DRE for detecting PCa were not high enough in a large meta-analysis study, at approximately 25.1% and 17.8%, respectively (3). Compared to the Western population, the Asian population, including the Taiwanese population, has a higher prevalence of PCa in the transitional zone (4, 5), which is less detectable by DRE.Elevated PSA is also found in several conditions, s...