Diagnostic Accuracy of Combination of Multiparametric MRI PI-RADS Score v2.1 and Prostate-Specific Antigen Density for Prostate Cancer Detection

Abstract

Introduction Prostate cancer (PCa) is the second most commonly diagnosed cancer in men worldwide. The Prostate Imaging-Reporting and Data System version 2.1 (PI-RADS v2.1) scoring system using multiparametric magnetic resonance imaging (mp-MRI) increases the accuracy for the assessment of clinically significant PCa. This study evaluates the diagnostic accuracy of a combination of PI-RADS v2.1 scores with prostate-specific antigen density (PSAD) for the detection of PCa, using biopsy outcomes as the gold standard, as well as the diagnostic accuracy of the combination of PI-RADS 3 lesion volume and PSAD. Methods This is single-center cross-sectional retrospective study including 54 subjects with serum PSA values > 4 ng/mL, who were referred for prostate mp-MRI. All patients underwent subsequent transrectal ultrasound (TRUS)-guided biopsy. Data collected includes PSA value, mp-MRI characteristics of the lesion, and histopathological findings. PI-RADS v2.1 score and PSAD were used to evaluate the diagnostic accuracy of this combination. Results In our study, the optimal PSAD cutoff was >0.18 with an area under the curve (AUC) of 0.897, indicating good diagnostic performance. The combination of PI-RADS v2.1 score ≥ 3 and PSAD ≥0.18 increased diagnostic accuracy, with a sensitivity of 96.97% and specificity of 71.43%. However, lesion volume was not a significant predictor of PCa. Conclusion In summary, our study demonstrates that the combination of PI-RADS score and PSAD yields higher diagnostic accuracy for the detection of PCa (p < 0.001) than using the PI-RADS score alone. We found an optimal PSAD cutoff of 0.18, which differs from the international consensus of 0.15. However, it cannot be used as a substitute for definitive pathological diagnosis but can be used in combination for better risk stratification, counselling, and management of patients with elevated PSA levels. Combining PI-RADS 3 lesion volume and PSAD did not have statistically significant results in our study.

Keywords: lesion volume; multiparameteric mri; pirads v2.1; prostate cancer; psa density.

Figure 1. Bar diagram showing Gleason score distribution

In the study, majority of subjects had a Gleason score of 3+3 (38.9%), followed by 4+3 (14.8%) and others.

Figure 2. ROC curve showing PSA density in predicting prostate malignancy

The ROC curve analysis for predicting prostate cancer showed that the AUC value of PSA density was 0.897 (95% CI: 0.787–0.962; p = 0.0001), suggesting that PSA density is a good marker for the diagnosis of prostate cancer. The ideal cutoff as per Youden’s index method was found to be >0.18, with a sensitivity of 91.4% and specificity of 81.8% in predicting prostate cancer. PSA, prostate-specific antigen; ROC, receiver operating characteristic

Figure 3. Reference case

A 63-year-old man presented with complaints of urinary incontinence. PSA was elevated at 5.9 ng/mL. On ultrasound examination, there was grade 1 prostatomegaly with features of cystitis. PSA density of 0.19 ng/mL/cc. MRI of the prostate was performed for further evaluation. T2-weighted axial section imaging (Figure 3A) showed an ill-defined hypointense area in the right posterior-lateral peripheral zone with hyperintensity on DWI (Figure 3B) and markedly low values on ADC (700-800x 10-6 mm²/s) (Figure 3C), without early or contemporaneous post-contrast enhancement, suggestive of a PI-RADS 3 lesion (Figure 3D). The lesion on histopathological examination was diagnosed as an adenocarcinoma. ADC, apparent diffusion coefficient; DWI, diffusion-weighted imaging; PI-RADS, Prostate Imaging-Reporting and Data System; PSA, prostate-specific antigen

Figure 4. Reference case

A 52-year-old man presented to the urology clinic with complaints of urinary incontinence. The serum analysis showed an elevated PSA of 7.6 ng/mL. Ultrasound examination demonstrated features of chronic cystitis with prostatomegaly.  Mp-MRI showed an enlarged prostate with a volume of 32 cc and PSA density of 0.23 ng/mL/cc. On T2-weighted axial section imaging (Figure 4A),  there was a lenticular area of hypointensity in the left anterior transition zone with hyperintensity on DWI (Figure 4B) and low values on ADC ( Figure 4C). DCE images demonstrated an early heterogenous enhancement within the lesion (Figure 4D), suggestive of a PI-RADS 4 lesion.  The lesion on histopathological examination was diagnosed as an adenocarcinoma. ADC, apparent diffusion coefficient; DCE, dynamic contrast-enhanced; DWI, diffusion-weighted imaging; PI-RADS, Prostate Imaging-Reporting and Data System; PSA, prostate-specific antigen