MRI of localized prostate cancer: coming of age in the PSA era

Abstract

Prostate cancer is the most common cancer among American men. It varies widely in aggressiveness, ranging from completely indolent to highly aggressive. Currently, predicting the natural history of a particular tumor and deciding on the appropriate treatment, which might include active surveillance, surgery, radiation or hormonal therapies, are based on the condition and age of the patient as well as the presumed stage of the disease. Imaging plays an important role in staging localized prostate cancer. Magnetic resonance imaging (MRI) best depicts the zonal anatomy, with a superior soft tissue resolution providing better results for tumor localization, monitoring, and local staging. Previously, the major function of prostate MRI has been in staging, and this role remains important. In this article, we introduce the reader to the expanding roles that MRI plays in the management of localized prostate cancer.

Figure 1. a, b.

Normal prostate anatomy. Axial T2W MR image (a) demonstrates a normal peripheral zone (P) that is hyperintense compared to the central gland (C) and is separated by a pseudocapsule (arrowhead); the true capsule of the prostate is seen as a hypointense rim (white arrows) with neurovascular bundles (black arrow); coronal T2W MR image (b) shows the seminal vesicles (white arrows) superior to the base of the prostate.

Figure 2.

Flowchart demonstrating the use of prostate MRI in several clinical scenarios. Route 1 (red) represents the current most common clinical use of MRI as a local staging tool after a positive biopsy and before treatment. Route 2 (purple) represents its use as a “screening tool” before biopsy. Route 3 (green) depicts its role as a “monitoring tool” in active surveillance. Route 4 (blue) represents its use as a “guidance tool” for patients with previous negative biopsies but rising serum PSA. Percentages denote the referral rate of each route on a per patient basis. PSA, prostate-specific antigen; DRE, digital rectal examination.

Figure 3. a–d.

Images from a 59-year-old patient with serum PSA of 8.71 ng/dL and a Gleason-score 3+3 (15% of core) tumor at the right base PZ detected by TRUS-guided biopsy prior to MRI. The axial T2W MR image (a) shows a hypointense lesion in the right mid-base peripheral zone (red asterisk); an ADC map of DW-MRI (b) shows restricted diffusion as a hypointense focus (red asterisk); MR spectroscopy (c) demonstrates an increased choline/citrate ratio within the lesion (white asterisks); and a quantitative map (d) obtained from DCE-MRI localizes the tumor (arrow). The patient underwent a TRUS-MRI-fusion-guided biopsy after MRI, and the right mid-base peripheral zone lesion was found to be upstaged to a Gleason-score 4+4 (90% of core) prostate cancer.

Figure 4. a–e.

Images from a 57-year-old patient with a PSA of 3.35 ng/dL and a Gleason-score 3+4 (70% of core) tumor at the right apical peripheral zone, detected by a TRUS-guided biopsy prior to MRI. The axial T2W MR image (a) shows a hypointense lesion in the right apical peripheral zone with extracapsular extension (arrow); an ADC map of DW-MRI (b) shows restricted diffusion as a hypointense focus (arrow) corresponding to the right apical peripheral zone lesion; MR spectroscopy (c) demonstrates an increased choline/citrate ratio within the lesion (white asterisk); and a raw DCE-MR image (d) and quantitative map (e) obtained from DCE-MRI localize the tumor (arrows in d and e).

Figure 5. a–e.

Images from a 43-year-old patient with a PSA of 30 ng/dL. The axial T2W MR image (a) shows a hypointense lesion in the left apical peripheral zone (red asterisk); an ADC map of DW-MRI (b) shows restricted diffusion as a hypointense focus (red asterisk) corresponding to the left apical peripheral zone lesion; the raw DCE-MR image (c) and the quantitative map (d) obtained from DCE-MRI localize the tumor (red asterisk in c, arrow in d); and an axial contrast-enhanced T1W image of the pelvis (e) shows an enlarged left iliac lymph node secondary to prostate cancer metastases (black asterisks).

Figure 6. a–d.

Images from a 50-year-old patient with a serum PSA of 15.8 ng/dL without any prior prostate biopsy history. The axial T2W MR image (a) shows a hypointense lesion in the right mid-base anterior central gland (red asterisk); an ADC map of DW-MRI (b) shows restricted diffusion within the lesion (red asterisk); and a raw DCE-MR image (c) and the quantitative map (d) obtained from DCE-MRI demonstrate early and fast enhancement within the lesion (red asterisks). The patient underwent TRUS-MRI-fusion-guided prostate biopsy, and the right mid-base anterior central gland lesion was found to contain Gleason-score 4+5 (100% of core) prostate cancer.

Figure 7. a–e.

Images from a 67-year-old patient with a serum PSA of 21.4 ng/dL with seven negative TRUS-guided prostate biopsies prior to MRI. The axial T2W MR image (a) shows a hypointense lesion in the mid-anterior central gland (arrow and red asterisk); an ADC map of DWMRI (b) shows restricted diffusion within the lesion (red asterisk); MR spectroscopy (c) demonstrates an increased choline/citrate ratio within the lesion (white asterisks); and a raw DCE-MR image (d) and the quantitative map (e) obtained from DCE-MRI demonstrate early and fast enhancement within the lesion (red asterisk). The patient underwent TRUS-MRI-fusion-guided prostate biopsy, and the mid-anterior central gland lesion was found to contain Gleason-score 3+4 (70% of core) prostate cancer.

Figure 8. a–f.

Images from a 82-year-old patient with a serum PSA of 4.9 ng/dL on active surveillance for a Gleason-score 3+4 (50% of core) tumor at the left mid-peripheral zone. The axial T2W MR image (a) shows a hypointense lesion in the left mid-anterior peripheral zone (arrow); an ADC map of DW-MRI (b) shows restricted diffusion within the lesion (arrow); and a raw DCE-MR image (c) demonstrates focal hyperenhancement within the lesion (arrow). One-year follow-up T2W MR images (d), ADC maps of DW-MRI (e), and DCE-MRI (f) demonstrate no change in MR imaging findings (arrows).

Figure 9. a–f.

Images from a 72-year-old patient with a serum PSA of 4.96 ng/dL on active surveillance for a Gleason-score 3+3 (30% of core) tumor at the right mid-peripheral zone. The axial T2W MR image (a) shows a hypointense lesion in the right mid-anterior peripheral zone (arrow); an ADC map of DW-MRI (b) shows restricted diffusion within the lesion (arrow); and a raw DCE-MR image (c) demonstrates focal hyper-enhancement within the lesion (arrow). The first-year follow-up T2W MR image (d), ADC map of DW-MRI (e), and DCEMRI (f) demonstrate a slight increase in lesion size (arrows). The serum PSA of the patient also increased to 7.9 ng/dL in the interval, and a repeat TRUS-MRI-fusion-guided biopsy after follow-up MRI revealed a Gleason-score 3+3 (50% of core) tumor in the right mid-anterior peripheral zone.

Figure 10. a–c.

Images from a 63-year-old-patient who had a radical prostatectomy eight years ago, recently with a serum PSA of 0.59 ng/dL. The axial T2W MR image (a) shows a slight intermediate signal-intensity focus in the right prostatectomy bed (arrow); the raw DCE-MRI (b) and quantitative map obtained from DCE-MRI (c) demonstrate focal, fast hyper-enhancement in the focus detected in the T2W MRI (arrows). The lesion was sampled via the TRUS-MRI-fusion biopsy approach, and the histopathology revealed recurrent prostate cancer.

Figure 11. a–c.

Images from a 70-old-patient who had focal cryoablation two years ago and had a recently measured serum PSA of 1.57 ng/dL. The axial T2W MR image (a) shows barely detectable hypointense lesions in the right mid-peripheral and central zones (red asterisks); an ADC map of DW-MRI (b) demonstrates restricted diffusion within both lesions (red asterisks); and a quantitative map obtained from DCE-MRI (c) demonstrates focal, fast hyper-enhancement in both lesions (red asterisks). The lesion was sampled via the TRUS-MRI-fusion biopsy approach, and the histopathology revealed moderately differentiated Gleason-score 3+3 (30% of core) recurrent prostate cancer.