Magnetic Resonance Elastography Combined With PI-RADS v2.1 for the Identification of Clinically Significant Prostate Cancer

Abstract

Background: Multiparametric MRI may cause overdiagnosis of clinically significant prostate cancer (csPCa) with the Prostate Imaging Reporting and Data System version 2.1 (PI-RADS v2.1).

Objectives: To investigate the diagnostic performance of stiffness as a standalone and complementary marker to PI-RADS v2.1 for diagnosing csPCa.

Study type: Prospective.

Subjects: One hundred forty-seven participants with pathologically confirmed prostate lesions (≥1 cm), including 71 with csPCa.

Field strength/sequence: T1-weighted fast spin-echo, T2-weighted fast spin-echo, single-shot echo-planar diffusion-weighted imaging, fast 3D gradient-echo T1-weighted dynamic contrast-enhanced imaging, and 3D single-shot spin-echo based echo-planar MR elastography at 3.0 T.

Assessment: The PI-RADS v2.1 score was assessed by three radiologists independently. Lesion shear stiffness (SS) values at 60 Hz and 90 Hz were measured. A modified PI-RADS integrating stiffness with PI-RADS v2.1 was developed. Diagnostic performance for csPCa was compared between stiffness, PI-RADS v2.1 and the modified PI-RADS.

Statistical test: Spearman's correlation, Fleiss κ and intraclass correlation, Pearson correlation, one-way analysis of variance, area under the receiver operating characteristic curve (AUC), and the Delong test. Significance level was P < 0.05.

Results: In the peripheral zone, csPCa (N = 35) had significantly higher SS than non-csPCa at 60 Hz (3.22 ± 0.66 kPa vs. 2.56 ± 0.56 kPa) and at 90 Hz (5.64 ± 1.30 kPa vs. 4.48 ± 0.84 kPa). PI-RADS v2.1 showed 100% sensitivity, 58% specificity, and 0.79 AUC for detecting csPCa. SS achieved 97% sensitivity, 52% specificity, and 0.80 AUC at 60 Hz, while SS had 63% sensitivity, 87% specificity, and 0.78 AUC at 90 Hz. The modified PI-RADS, combing SS at 60 Hz with PI-RADS v2.1, resulted in a significantly increased AUC (0.86) compared to that of PI-RADS v2.1, with a sensitivity of 97% and specificity of 75%.

Data conclusion: Stiffness can help identifying csPCa in the peripheral zone. Combining stiffness with the PI-RADS v2.1 improved the diagnostic accuracy and specificity for csPCa.

Evidence level: 1 TECHNICAL EFFICACY: Stage 2.

Keywords: Prostate Imaging Reporting and Data System; clinically significant prostate cancer; elastography.

Figure 1.

Schematic representation of the modified PI-RADS scoring system incorporating separate apparent diffusion coefficient (ADC), shear stiffness at 60Hz and 90Hz, respectively.

Figure 2.

Flow chart of participants’ inclusion and exclusion.

Figure 3.

Boxplots of shear stiffness by MRE at 60Hz and 90Hz for benign prostatic lesions, indolent prostate cancer (PCa), and clinically significant PCa (csPCa) located at different anatomical regions.

Figure 4.

Representative axial T2-weighted images (T2WI), diffusion-weighted images (DWI) at b value of 1400 s/mm², corresponding apparent diffusion coefficient (ADC) map, MR elastography magnitude image, and corresponding shear stiffness at 60Hz and 90Hz for three patients. A, a 77-year-old patient with chronic prostatitis. B, a 49-year-old patient with indolent prostate cancer with a Gleason score of 3+3. C, a 57-year-old patient with clinically significant prostate cancer with a Gleason score of 4+5.

Figure 5.

Receiver operating characteristic curves for assessing diagnostic performance in identifying clinically significant prostate cancer located at the peripheral zone using the consensus-reached PI-RADS v2.1 score, apparent diffusion coefficient (ADC), shear stiffness at 60Hz mechanical frequency, and shear stiffness at 90Hz mechanical frequency.

Figure 6.

Bland-Altman plots showing inter-reviewer agreement of apparent diffusion coefficient (A), shear stiffness at 60Hz mechanical frequency (B) and shear stiffness at 90Hz mechanical frequency (C) from 2 readers in all participants. ICC, intraclass correlation coefficients; LOA, limit of agreement.