Multiparametric MRI - local staging of prostate cancer and beyond

Abstract

Background Accurate local staging is critical for treatment planning and prognosis in patients with prostate cancer (PCa). The primary aim is to differentiate between organ-confined and locally advanced disease with the latter carrying a worse clinical prognosis. Multiparametric MRI (mpMRI) is the imaging modality of choice for the local staging of PCa and has an incremental value in assessing pelvic nodal disease and bone involvement. It has shown superior performance compared to traditional staging based on clinical nomograms, and provides additional information on the site and extent of disease. MRI has a high specificity for diagnosing extracapsular extension (ECE), seminal vesicle invasion (SVI) and lymph node (LN) metastases, however, sensitivity remains poor. As a result, extended pelvic LN dissection remains the gold standard for assessing pelvic nodal involvement, and there has been recent progress in developing advanced imaging techniques for more distal staging. Conclusions T2W-weighted imaging is the cornerstone for local staging of PCa. Imaging at 3T and incorporating both diffusion weighted and dynamic contrast enhanced imaging can further increase accuracy. "Next generation" imaging including whole body MRI and PET-MRI imaging using prostate specific membrane antigen (68Ga-PSMA), has shown promising for assessment of LN and bone involvement as compared to the traditional work-up using bone scintigraphy and body CT.

Keywords: multiparametric MRI; prostate cancer; staging.

Figure 1

65-yr-old man with PSA 19.5 ng/ml. Invasion of the periprostatic fat and neurovascular bundle (NVB) infiltration at the left midgland consistent with T3a disease. Biopsy showed Gleason score (GS) 4 + 4 = 8. Radical retropubic prostatectomy (RRP) confirmed GS 4 + 4 = 8 and showed established T3a disease with a clear surgical margin (at least 1 mm).

Figure 2

77-yr-old man with PSA 38.2 ng/ml. (A) T2 weighted (T2W) imaging; (B) diffusion weighted (DW) imaging: (C) apparent diffusion coefficient (ADC) map. T3a at the right mid gland with bulging and asymmetrical thickening of the right neurovascular bundle (arrow). Gleason score (GS) = 9 with extracapsular extension and clear surgical margins was confirmed at radical prostatectomy.

Figure 3

74-yr-old man with PSA 35.2 ng/ml. (A) T2 weighted (T2W) imaging, (B) diffusion weighted (DW) imaging, (C) apparent diffusion coefficient (ADC) map. T3a at the right mid gland as suggested by a broad capsular contact at 19.4 mm. Biopsy showed Gleason score (GS) 4 + 4 = 8 disease. Patient underwent radiotherapy.

Figure 4

57-yr-old man with PSA 26 ng/ml. (A) Axial T2 weighted imaging (T2WI) shows mid gland right peripheral zones (PZ) lesion (arrow) with capsular contact but no tumour extension beyond it. (B) axial thin-sliced cube reformat suggests capsular breach and right neurovascular bundle involvement (arrow). Prostatectomy showed tumour in the right mid gland, Gleason score 4 + 5 = 9, with established extracapsular extension (ECE) (pT3a).

Figure 5

65-yr-old-man with PSA = 15.3 ng/ml and Gleason score 4 + 4 = 8 at biopsy. Axial (A) and coronal (C) T2 weighted imaging (T2WI) and diffusion weighted imaging (DWI) (B). T3b involving both seminal vesicles via ejaculatory ducts, shown in the coronal plane (arrow).

Figure 6

67-yr-old man with raising PSA = 12.7 ng/ml. (A) (coronal) and (B) (axial) T2 weighted (T2W) imaging shows index lesion in the left apex (*) and a low signal focus in the left seminal vesicle (arrow) with corresponding restricted diffusion on diffusion weighted imaging (DWI) ((C); arrow) and apparent diffusion coefficient (ADC) map ((D); arrow).

Figure 7

55-yr-old-man with PSA 32 ng/ml. (A) T2 weighted (T2W) imaging, (B) T1 weighted (T1W) imaging, (C) diffusion weighted (DW) imaging, (D) apparent diffusion coefficient (ADC) map. Low T2 signal in the right seminal vesicle is mimicking prostate cancer (D), however, there is no restricted diffusion. Biopsy of the right seminal vesicle showed amyloidosis which was confirmed at radical prostatectomy. Index tumour with Gleason score 4 + 3 = 7 was in the left peripheral zone.

Figure 8

77-yr-old man with PSA = 38.2 ng/ml. Enlarged nodes bilaterally consistent with metastatic involvement on T2 weighted imaging (T2WI) (A), more conspicuous on diffusion weighted imaging (DWI) (B).

Figure 9

61-yr-old man with PSA = 12.7 ng/ml. Bone metastasis (arrow) in the right sacrum shown as low signal on T1 weighted (T1W) imaging (A); more conspicuous as high signal on diffusion weighted imaging (DWI) (B).