Feasibility of multiparametric prostate magnetic resonance imaging in the detection of cancer distribution: histopathological correlation with prostatectomy specimens

Abstract

Purpose: To prevent overtreatment, it is very important to diagnose the precise distribution and characteristics of all cancer lesions, including small daughter tumors. The purpose of this study was to evaluate the efficacy of T2-weighted magnetic resonance imaging (T2W), diffusion-weighted magnetic resonance imaging (DWI), magnetic resonance spectroscopy ((1)H-MRS), and prostate biopsy (PBx) in the detection of intraprostatic cancer distribution.

Methods: All patients underwent T2W, DWI, (1)H-MRS, and PBx followed by radical prostatectomy (RP). Individual prostates were divided into 12 segmental regions, each of which was examined for the presence or absence of malignancy on the basis of T2W, DWI, (1)H-MRS, and PBx, respectively. These results were compared with the histopathological findings for RP specimens.

Results: We included 54 consecutive patients with biopsy-proven prostate cancer (mean age, 62.7 years; median prostate-specific antigen level, 5.7 ng/mL) in this study. We could detect cancer in 247 of 540 evaluable lesions. The area under the receiver operator characteristic curve analysis yielded a higher value for DWI (0.68) than for T2W (0.65), (1)H-MRS (0.54), or PBx (0.56). In 180 cancerous regions of RP specimens with false-negative PBx results, T2W+DWI had the highest positive rate (53.3%) compared with that of each sequence alone, including T2W (45.6%), DWI (41.1%), and (1)H-MRS (30.0%).

Conclusions: Multiparametric magnetic resonance imaging (T2W, (1)H-MRS, DWI) enables the detection of prostate cancer distribution with reasonable sensitivity and specificity. T2W+DWI was particularly effective in detecting cancer distribution with false-negative PBx results.

Keywords: Diffusion magnetic resonance imaging; Magnetic resonance imaging; Magnetic resonance spectroscopy; Prostate neoplasms.

Fig. 1.

Prostate cancer (PCa) in a 68-year-old man with an initial prostate-specific antigen value of 14 ng/mL. (A) Radical prostatectomy (RP) specimen: histopathologic findings at the peripheral zone at the midprostate level indicate tumor presence (Gleason score, 4+3); the diagonal red lines indicate the presence of PCa on the basis of histopathological findings. The remaining panels (B–D) correspond to the slices of the RP specimen. (B) Axial T2-weighted magnetic resonance imaging (T2W) image demonstrating a mass of homogeneously low signal intensity with ill-defined margins (red arrow). (C) Diffusion-weighted magnetic resonance imaging image demonstrates a mass of hyper-signal intensity (red arrow). (D) Magnetic resonance spectroscopy imaging shows abnormal metabolism characterized by high choline and low citrate peaks in the region of the T2W abnormality (red area). Red dotted-line boxes indicate the regions suggestive of malignancy. Blue dotted-line boxes indicate the normal findings suggestive of benign regions.

Fig. 2.

Each prostate was divided into 12 segmented regions. For tumor localization, each prostate was divided into halves: right and left. Each half was further divided into 6 regions as follows: (A) outside peripheral zone (Pz) anterior, (B) outside Pz posterior, (C) inside Pz, (D) central transitional zone (Tz), (E) Tz anterior, (F) apex.

Fig. 3.

Diagnostic accuracy. (A) The diagnostic accuracy of each sequence alone and multiparametric magnetic resonance imaging (MRI) in all segmental regions. (B) The diagnostic accuracy only in segmental regions of peripheral zone (Pz). PPV, positive predictive value; NPV, negative predictive value; AUC, areas under the receiver operator curve; T2W, T2-weighted MRI; DWI, diffusion-weighted magnetic resonance imaging; ¹H-MRS, magnetic resonance spectroscopy; PBx, prostate biopsy.

Fig. 4.

Results of the region of Interest analysis for T2-weighted magnetic resonance imaging (T2W), diffusion-weighted magnetic resonance imaging (DWI), magnetic resonance spectroscopy (¹H-MRS), and prostate biopsy (PBx). Area under the receiver operator characteristic curve (AUC) analysis found that DWI had a higher AUC of 0.68 compared with T2W (0.65), ¹H-MRS (0.54), and PBx (0.56). TPF, true positive fraction; FPF, false positive fraction.

Fig. 5.

Of 247 cancerous regions in radical prostatectomy (RP) specimens, 180 could not be diagnosed by prostate biopsy (PBx). In 180 cancerous regions of RP specimens with negative PBx results, T2-weighted magnetic resonance imaging (T2W)+diffusion-weighted magnetic resonance imaging (DWI) had the highest positive rate (53.3%) compared with T2W alone (45.6%), DWI alone (41.1%), and magnetic resonance spectroscopy (¹H-MRS) alone (30.0%).

Fig. 6.

The positive rate of each sequence alone by Gleason score. The positive rate of diffusion-weighted magnetic resonance imaging (DWI; A) and T2-weighted magnetic resonance imaging (T2W; B) increased with increasing Gleason score. In contrast, regardless of Gleason score, the positive rate of prostate biopsy (PBx; D) remained cons istently low. ¹H-MRS, magnetic resonance spectroscopy.