Multiparametric MR Imaging of the Prostate after Treatment of Prostate Cancer

Abstract

The use of multiparametric magnetic resonance (MR) imaging in prostate cancer therapy is increasing, as newer treatment methods and management approaches emerge. The mainstays of therapy-radiation and surgery-are being supplemented (and even replaced) by novel focal therapy methods. Laser and ultrasonographic ablation, photodynamic therapy, electroporation, and cryoablation are the most common focal therapies, each with its own imaging findings. Typical ablation zones have a central focus of enhancement with peripheral rim enhancement; thus, dynamic contrast material-enhanced (DCE) MR imaging is the most important sequence for evaluation of treatment in the immediate posttherapeutic setting. Detection of recurrence can initiate salvage therapy, but recurrence can be difficult to detect on T2-weighted images, again necessitating DCE MR imaging and also diffusion-weighted imaging. Furthermore, the location of recurrence can vary depending on the therapy. With radiation therapy, the most common site of recurrence is the prior tumor site, whereas after prostatectomy, the recurrence usually occurs around the vesicoureteral anastomosis. Regarding management, there is an increased emphasis on watchful waiting and active surveillance, for which MR imaging has a critical role in both selection and follow-up of patients who undergo active surveillance. As MR imaging is being increasingly used for imaging suspected recurrence, it is important for radiologists to be familiar with the normal posttreatment findings and patterns and MR imaging findings of recurrence. RSNA, 2018.

Multiparametric MRI Approach to Prostate Cancer with a Pictorial Essay on PI-RADS

“…Mp-MRI, especially diffusion-weighted imaging (DWI) and DCE, plays a role in selection of patients for surveillance, imaging the posttreatment prostate, and detection of recurrence. 12 Mp-MRI offers a higher negative predictive value than systematic biopsy as was shown in the prostate MRI Study (PROMIS) trial, (89% vs. 74%). 11 ACR (American College of Radiology) appropriateness criteria rate MRI as "usually appropriate" with a rating scale of 7 for clinically suspected prostate cancer in biopsy-naïve patients and a higher rating scale of 8 for clinically suspected prostate cancer with prior negative transrectal ultrasound-guided biopsy; for surveillance in low-risk cancer; for staging and/ or surveillance in intermediate-risk prostate cancer; and for staging in high-risk cancer.…”

Optimizing patient selection for focal therapy—mapping and ablating the index lesion

“…Although these early results do not predict treatment success, the ability of early follow-up MRI to assess gross targeting may be useful during the initial adoption of an ablative treatment. Surveillance mpMRI using contrast enhancement assesses for viable tissue within or around the treatment zone by assessing for enhancement on post-contrast T1 imaging ( 38 ). Post-ablation, DCE imaging appears to be more sensitive than DWI for detection of local recurrence ( 39 ).…”

“…Post-ablation, DCE imaging appears to be more sensitive than DWI for detection of local recurrence ( 39 ). However, follow up imaging characteristics vary by the type of ablation energy utilized ( 38 ).…”

18F-Fluciclovine Parameters on Targeted Prostate Biopsy Associated with True Positivity in Recurrent Prostate Cancer

“…BCR is frequently detectable before clinical evidence of recurrent disease is seen. Diagnosis of recurrent prostate cancer after localized therapy is challenging because of significant changes in the prostate anatomy and the presence of artifacts from previous definitive treatment (4,5). Transrectal ultrasound (TRUS)-guided biopsy, the standard method for recurrent cancer detection in the prostate or prostate bed, has several limitations, including a low detection rate and low accuracy (6)(7)(8).…”

“…Imaging has achieved a prominent role in the diagnosis of recurrent prostate cancer. MRI is of great value in the detection of primary prostate cancer yet has suboptimal diagnostic performance for recurrent prostate cancer detection (9)(10)(11), partly because of tissue changes from previous treatment (4,5). Molecular imaging using radiotracers such as 18 F-and 11 C-choline (12)(13)(14), 68 Ga-prostate-specific membrane antigen (15,16), and 18 F-fluciclovine (17)(18)(19)(20)(21)(22)(23) has also been applied for the detection and localization of recurrent prostate cancer.…”