Comparative sensitivities of functional MRI sequences in detection of local recurrence of prostate carcinoma after radical prostatectomy or external-beam radiotherapy

Magnetic Resonance Imaging Techniques for Post-Treatment Evaluation After External Beam Radiation Therapy of Prostate Cancer: Narrative Review

Background/Objectives: This study aimed to investigate the prognostic value of advanced techniques of magnetic resonance imaging (MRI) biochemical recurrence (BCR) after radiotherapy in patients with prostate cancer (PCa). Methods: A comprehensive literature review was conducted to evaluate the role of MRI in detecting BCR of PCa patients after external beam radiation therapy. Results: National guidelines do not recommend imaging techniques in clinical follow-up PCa. However, in 2021, the European Association of Urogenital Radiology (ESUR), the European Association of Urological Imaging (ESUI), and the PI-RADS Steering Committee introduced the Prostate Imaging for Recurrence Reporting (PI-RR) system. PI-RR incorporates the MRI biomarkers in the post-treatment process. In the last decade, a growing number of clinical researchers have investigated the role of various MRI techniques in BCR. Conclusions: The integration of advanced MRI technologies into clinical routine marks the beginning of a new era of BCR with accuracy.

Application of next-generation imaging in biochemically recurrent prostate cancer

BACKGROUND

Biochemical recurrence (BCR) following primary interventional treatment occurs in approximately one-third of patients with prostate cancer (PCa). Next-generation imaging (NGI) can identify local and metastatic recurrence with greater sensitivity than conventional imaging, potentially allowing for more effective interventions. This narrative review examines the current clinical evidence on the utility of NGI for patients with BCR.

METHODS

A search of PubMed was conducted to identify relevant publications on NGI applied to BCR. Given other relevant recent reviews on the topic, this review focused on papers published between January 2018 to May 2023.

RESULTS

NGI technologies, including positron emission tomography (PET) radiotracers and multiparametric magnetic resonance imaging, have demonstrated increased sensitivity and selectivity for diagnosing BCR at prostate-specific antigen (PSA) concentrations <2.0 ng/ml. Detection rates range between 46% and 50%, with decreasing PSA levels for choline (1-3 ng/ml), fluciclovine (0.5-1 ng/ml), and prostate-specific membrane antigen (0.2-0.49 ng/ml) PET radiotracers. Expert working groups and European and US medical societies recommend NGI for patients with BCR.

CONCLUSIONS

Available data support the improved detection performance and selectivity of NGI modalities versus conventional imaging techniques; however, limited clinical evidence exists demonstrating the application of NGI to treatment decision-making and its impact on patient outcomes. The emergence of NGI and displacement of conventional imaging may require a reexamination of the current definitions of BCR, altering our understanding of early recurrence. Redefining the BCR disease state by formalizing the role of NGI in patient management decisions will facilitate greater alignment across research efforts and better reflect the published literature.

MRI and PSMA PET/CT of Biochemical Recurrence of Prostate Cancer

Prostate cancer may recur several years after definitive treatment, such as prostatectomy or radiation therapy. A rise in serum prostate-specific antigen (PSA) level is the first sign of disease recurrence, and this is termed biochemical recurrence. Patients with biochemical recurrence have worse survival outcomes. Radiologic localization of recurrent disease helps in directing patient management, which may vary from active surveillance to salvage radiation therapy, androgen-deprivation therapy, or other forms of systemic and local therapy. The likelihood of detecting the site of recurrence increases with higher serum PSA level. MRI provides optimal diagnostic performance for evaluation of the prostatectomy bed. Prostate-specific membrane antigen (PSMA) PET radiotracers currently approved by the U.S. Food and Drug Administration demonstrate physiologic urinary excretion, which can obscure recurrence at the vesicourethral junction. However, MRI and PSMA PET/CT have comparable diagnostic performance for evaluation of local recurrence after external-beam radiation therapy or brachytherapy. PSMA PET/CT outperforms MRI in identifying recurrence involving the lymph nodes and bones. Caveats for use of both PSMA PET/CT and MRI do exist and may cause false-positive or false-negative results. Hence, these techniques have complementary roles and should be interpreted in conjunction with each other, taking the patient history and results of any additional prior imaging studies into account. Novel PSMA agents at various stages of investigation are being developed, and preliminary data show promising results; these agents may revolutionize the landscape of prostate cancer recurrence imaging in the future. ©RSNA, 2023 Quiz questions for this article are available through the Online Learning Center. See the invited commentary by Turkbey in this issue. The slide presentation from the RSNA Annual Meeting is available for this article.

Dynamic Contrast-Enhanced Study in the mpMRI of the Prostate-Unnecessary or Underutilised? A Narrative Review

The aim of this review is to summarise recent scientific literature regarding the clinical use of DCE-MRI as a component of multiparametric resonance imaging of the prostate. This review presents the principles of DCE-MRI acquisition and analysis, the current role of DCE-MRI in clinical practice with special regard to its role in presently available categorisation systems, and an overview of the advantages and disadvantages of DCE-MRI described in the current literature. DCE-MRI is an important functional sequence that requires intravenous administration of a gadolinium-based contrast agent and gives information regarding the vascularity and capillary permeability of the lesion. Although numerous studies have confirmed that DCE-MRI has great potential in the diagnosis and monitoring of prostate cancer, its role is still inadequate in the PI-RADS categorisation. Moreover, there have been numerous scientific discussions about abandoning the intravenous application of gadolinium-based contrast as a routine part of MRI examination of the prostate. In this review, we summarised the recent literature on the advantages and disadvantages of DCE-MRI, focusing on an overview of currently available data on bpMRI and mpMRI, as well as on studies providing information on the potential better usability of DCE-MRI in improving the sensitivity and specificity of mpMRI examinations of the prostate.

ACR Appropriateness Criteria® Post-Treatment Follow-up of Prostate Cancer: 2022 Update

Prostate cancer has a wide spectrum ranging between low-grade localized disease and castrate-resistant metastatic disease. Although whole gland and systematic therapies result in cure in the majority of patients, recurrent and metastatic prostate cancer can still occur. Imaging approaches including anatomic, functional, and molecular modalities are continuously expanding. Currently, recurrent and metastatic prostate cancer is grouped in three major categories: 1) Clinical concern for residual or recurrent disease after radical prostatectomy, 2) Clinical concern for residual or recurrent disease after nonsurgical local and pelvic treatments, and 3) Metastatic prostate cancer treated by systemic therapy (androgen deprivation therapy, chemotherapy, immunotherapy). This document is a review of the current literature regarding imaging in these settings and the resulting recommendations for imaging. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Mapping of Local Recurrences After Radical Prostatectomy Using 68-Gallium-Prostate-Specific Membrane Antigen Positron Emission Tomography/Computed Tomography: Implications for Postprostatectomy Radiation Therapy Clinical Target Volumes

PURPOSE

Our objective is to describe the distribution of local recurrences after radical prostatectomy (RP) as delineated using 68-Gallium-prostate-specific membrane antigen positron emission tomography/computed tomography (⁶⁸Ga-PSMA PET/CT) to identify areas where current consensus guideline clinical target volumes (CTVs) are insufficient or excessive and to identify predictors of recurrence location within the fossa.

METHODS AND MATERIALS

Retrospective review of databases from 2 tertiary referral centers was performed to identify patients who underwent ⁶⁸Ga-PSMA PET/CT for biochemical recurrence after RP. Those with a component of local recurrence were included for further analysis. The epicenter of each recurrence was defined relative to reference points in 3 axes, categorized into 1 of 7 levels in the superior/inferior axis relative to the vesicourethral anastomosis, and recorded as within or outside the Faculty of Radiation Oncology Genito-urinary Group (FROGG) and Radiation Therapy Oncology Group consensus CTVs. Univariate and multivariate analysis was performed to identify predictors of recurrence location based on clinical and histopathologic variables.

RESULTS

One thousand forty-nine ⁶⁸Ga-PSMA PET/CT scans were reviewed. One hundred forty sites of local recurrence were identified on 132 scans. Relative to the vesicourethral anastomosis, 13 (9%), 31 (22%), 17 (12%), 24 (17%), 27 (19%), 20 (14%), and 8 (6%) recurrences occurred >5 mm inferior; within 5 mm above or below; and 6 to 15 mm, 16 to 25 mm, 26 to 35 mm, 36 to 45 mm, and >45 mm superiorly, respectively. Thirteen (9%) and 2 (1.4%) recurrences occurred beyond the FROGG and Radiation Therapy Oncology Group consensus CTVs, respectively, with all below the inferior CTV margin.

CONCLUSIONS

In the largest study to date mapping local recurrences after RP in 3-dimensions, we provide several insights to inform future contouring guidelines; in particular, 9% of recurrences occurred inferior to the FROGG CTV.

Prostate Multiparametric MRI: Evaluation of Recurrence and Post-treatment Changes

Purpose of Review

This article reviews all the most common therapeutic strategies of prostate cancer, systemic or local, and all the following morpho-structural alterations, with the aim of helping the radiologist to recognize the signs of recurrence by using mp-MRI.

Recent Findings

According to the most recent evidences, prostate mp-MRI has now become a strong, non-invasive, and valid tool to evaluate all patient treated for prostatic carcinoma across the time, especially in the suspicion of biochemical recurrence.

Summary

The minimal signs of focal recurrence can put a strain on radiologists, especially if they are novice with multi-parametric prostate MRI. Familiarizing themselves with the outcomes of treatment, local or systemic, and its characteristics to MR imaging is indispensable to avoid diagnostic pitfalls and, subsequently, unnecessary reinterventions.

The role of MRI in prostate cancer: current and future directions

There has been an increasing role of magnetic resonance imaging (MRI) in the management of prostate cancer. MRI already plays an essential role in the detection and staging, with the introduction of functional MRI sequences. Recent advancements in radiomics and artificial intelligence are being tested to potentially improve detection, assessment of aggressiveness, and provide usefulness as a prognostic marker. MRI can improve pretreatment risk stratification and therefore selection of and follow-up of patients for active surveillance. MRI can also assist in guiding targeted biopsy, treatment planning and follow-up after treatment to assess local recurrence. MRI has gained importance in the evaluation of metastatic disease with emerging technology including whole-body MRI and integrated positron emission tomography/MRI, allowing for not only better detection but also quantification. The main goal of this article is to review the most recent advances on MRI in prostate cancer and provide insights into its potential clinical roles from the radiologist's perspective. In each of the sections, specific roles of MRI tailored to each clinical setting are discussed along with its strengths and weakness including already established material related to MRI and the introduction of recent advancements on MRI.

Defining Prostatic Vascular Pedicle Recurrence and the Anatomy of Local Recurrence of Prostate Cancer on Prostate-specific Membrane Antigen Positron Emission Tomography/Computed Tomography

Background

The term local recurrence in prostate cancer is considered to mean persistent local disease in the prostatic bed, most commonly at the site of the vesicourethral anastomosis (VUA). Since the introduction of prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) and magnetic resonance imaging for assessment of early biochemical recurrence (BCR), we have found histologically confirmed prostate cancer in the prostatic vascular pedicle (PVP). If a significant proportion of local recurrences are distant to the VUA, it may be possible to alter adjuvant and salvage radiation fields in order to reduce the potential morbidity of radiation in selected patients.

Objective

To describe PVP local recurrence and to map the anatomic pattern of prostate bed recurrence on PSMA PET/CT.

Design, setting, and participants

This was a retrospective multicentre study of 185 patients imaged with PSMA PET/CT following radical prostatectomy (RP) between January 2016 and November 2018. All patient data and clinical outcomes were prospectively collected. Recurrences were documented according to anatomic location. For patients presenting with local recurrence, the precise location of the recurrence within the prostate bed was documented.

Intervention

PSMA PET/CT for BCR following RP.

Results and limitations

A total of 43 local recurrences in 41/185 patients (22%) were identified. Tumour recurrence at the PVP was found in 26 (63%), VUA in 15 (37%), and within a retained seminal vesicle and along the anterior rectal wall in the region of the neurovascular bundle in one (2.4%) each. Histological and surgical evidence of PVP recurrence was acquired in two patients. The study is limited by its retrospective nature with inherent selection bias. This is an observational study reporting on the anatomy of local recurrence and does not include follow-up for patient outcomes.

Conclusions

Our study showed that prostate cancer can recur in the PVP and is distant to the VUA more commonly than previously thought. This may have implications for RP technique and for the treatment of selected patients in the local recurrence setting.

Patient summary

We investigated more precise identification of the location of tumour recurrence after removal of the prostate for prostate cancer. We describe a new definition of local recurrence in an area called the prostatic vascular pedicle. This new concept may alter the treatment recommended for recurrent disease.

Diagnostic Accuracy and Observer Agreement of the MRI Prostate Imaging for Recurrence Reporting Assessment Score

Background Prostate cancer local recurrence location and extent must be determined in an accurate and timely manner. Because of the lack of a standardized MRI approach after whole-gland treatment, a panel of international experts recently proposed the Prostate Imaging for Recurrence Reporting (PI-RR) assessment score. Purpose To determine the diagnostic accuracy of PI-RR for detecting local recurrence in patients with biochemical recurrence (BCR) after radiation therapy (RT) or radical prostatectomy (RP) and to evaluate the interreader variability of PI-RR scoring. Materials and Methods This retrospective observational study included patients who underwent multiparametric MRI between September 2016 and May 2021 for BCR after RT or RP. MRI scans were analyzed, and a PI-RR score was assigned independently by four radiologists. The reference standard was defined using histopathologic findings, follow-up imaging, or clinical response to treatment. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were calculated to assess PI-RR performance for each reader. The intraclass correlation coefficient was used to determine interreader agreement. Results A total of 100 men were included: 48 patients after RT (median age, 76 years [IQR, 70-82 years]) and 52 patients after RP (median age, 70 years [IQR, 66-74 years]). After RT, with PI-RR of 3 or greater as a cutoff (assigned when recurrence is uncertain), diagnostic performance ranges were 71%-81% sensitivity, 74%-93% specificity, 71%-89% PPV, 79%-86% NPV, and 77%-88% accuracy across the four readers. After RP, with PI-RR of 3 or greater as a cutoff, performance ranges were 59%-83% sensitivity, 87%-100% specificity, 88%-100% PPV, 66%-80% NPV, and 75%-85% accuracy. The intraclass correlation coefficient was 0.87 across the four readers for both the RT and RP groups. Conclusion MRI scoring with the Prostate Imaging for Recurrence Reporting assessment provides structured, reproducible, and accurate evaluation of local recurrence after definitive therapy for prostate cancer. © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Haider in this issue.

MR Imaging in Real Time Guiding of Therapies in Prostate Cancer

Magnetic resonance imaging (MRI)-guided therapy for prostate cancer (PCa) aims to reduce the treatment-associated comorbidity of existing radical treatment, including radical prostatectomy and radiotherapy. Although active surveillance has been used as a conservative method to reduce overtreatment, there is a growing demand for less morbidity and personalized (focal) treatment. The development of multiparametric MRI was of real importance in improving the detection, localization and staging of PCa. Moreover, MRI has been useful for lesion targeting within the prostate, as it is used in the guidance of prostate biopsies, by means of cognitive registration, MRI-ultrasound fusion guidance or direct in-bore MRI-guidance. With regard to PCa therapies, MRI is used for precise probe placement into the lesion and to accurately monitor the treatment in real-time. Moreover, advances in MR-compatible thermal ablation allow for noninvasive real-time temperature mapping during treatment. In this review, we present an overview of the current status of MRI-guided therapies in PCa, focusing on cryoablation, focal laser ablation, high intensity focused ultrasound and transurethral ultrasound ablation. We explain the important role of MRI in the evaluation of the completeness of the ablation and during follow-up. Finally, we will discuss the challenges and future development inherent to these new technologies.

Prostate cancer: Molecular imaging and MRI

The role of molecular imaging in initial evaluation of men with presumed or established diagnosis of prostate cancer and work up of biochemical recurrence and metastatic disease is rapidly evolving due to superior diagnostic performance compared to anatomic imaging. However, variable tumor biology and expression of transmembrane proteins or metabolic alterations poses a challenge. We review the evidence and controversies with emphasis on emerging PET radiopharmaceuticals and experience on clinical utility of PET/CT and PET/MRI in diagnosis and management of prostate cancer.

Value of PET imaging for radiation therapy

This comprehensive review written by experts in their field gives an overview on the current status of incorporating positron emission tomography (PET) into radiation treatment planning. Moreover, it highlights ongoing studies for treatment individualisation and per-treatment tumour response monitoring for various primary tumours. Novel tracers and image analysis methods are discussed. The authors believe this contribution to be of crucial value for experts in the field as well as for policy makers deciding on the reimbursement of this powerful imaging modality.

MR compatibility, safety and accuracy of the redesigned UMC Utrecht single needle implant device

Purpose. The Utrecht single needle implant device (SNID) was redesigned to increase needle insertion velocity. The purpose of this study is to evaluate the magnetic resonance compatibility, safety and accuracy of the implant device preparing its application in a patient study to investigate the feasibility of inserting a brachytherapy needle into the prostate to a defined tumor target point.Methods. Several experiments were performed to evaluate the mechanical and radiofrequency safety of the needle system, the magnetic field perturbation, the calibration of the implant device in the MR coordinate system, functioning of the implant device during imaging and accuracy of needle insertion.Results. Endurance experiments showed the mechanical safety of the needle system. Magnetic field perturbation was acceptable with induced image distortions smaller than 0.5 mm for clinical MR sequences. Calibration of the implant device in the MR coordinate system was reproducible with average error (mean±standard deviation) of 0.2 ± 0.4 mm, 0.1 ± 0.3 mm and 0.6 ± 0.6 mm in thex,y- andz- direction, respectively. The RF safety measurement showed for clinical MR imaging sequences maximum temperature rises of 0.2 °C at the entry and tip points of the needle. Simultaneous functioning of the implant device and imaging is possible albeit with some intensity band artifacts in the fast field echo images. Finally, phantom measurements showed deviations amounting 2.5-3.6 mm measured as target-to-needle distance at a depth of 12 cm.Conclusions. This preclinical evaluation showed that the MR compatibility, safety and accuracy of the redesigned UMC Utrecht SNID allow its application in a patient study on the feasibility of inserting a brachytherapy needle into the prostate to a defined tumor target point.

Artificial intelligence and imaging biomarkers for prostate radiation therapy during and after treatment

Magnetic resonance imaging (MRI) is increasingly used in the management of prostate cancer (PCa). Quantitative MRI (qMRI) parameters, derived from multi-parametric MRI, provide indirect measures of tumour characteristics such as cellularity, angiogenesis and hypoxia. Using Artificial Intelligence (AI), relevant information and patterns can be efficiently identified in these complex data to develop quantitative imaging biomarkers (QIBs) of tumour function and biology. Such QIBs have already demonstrated potential in the diagnosis and staging of PCa. In this review, we explore the role of these QIBs in monitoring treatment response during and after PCa radiotherapy (RT). Recurrence of PCa after RT is not uncommon, and early detection prior to development of metastases provides an opportunity for salvage treatments with curative intent. However, the current method of monitoring treatment response using prostate-specific antigen levels lacks specificity. QIBs, derived from qMRI and developed using AI techniques, can be used to monitor biological changes post-RT providing the potential for accurate and early diagnosis of recurrent disease.

Detection and staging of radio-recurrent prostate cancer using multiparametric MRI

OBJECTIVE

We determined the sensitivity and specificity of multiparametric magnetic resonance imaging (MP-MRI) in detection of locally recurrent prostate cancer and extra prostatic extension in the post-radical radiotherapy setting. Histopathological reference standard was whole-mount prostatectomy specimens. We also assessed for any added value of the dynamic contrast enhancement (DCE) sequence in detection and staging of local recurrence.

METHODS

This was a single centre retrospective study. Participants were selected from a database of males treated with salvage prostatectomy for locally recurrent prostate cancer following radiotherapy. All underwent pre-operative prostate-specific antigen assay, positron emission tomography CT, MP-MRI and transperineal template prostate mapping biopsy prior to salvage prostatectomy. MP-MRI performance was assessed using both Prostate Imaging-Reporting and Data System v. 2 and a modified scoring system for the post-treatment setting.

RESULTS

24 patients were enrolled. Using Prostate Imaging-Reporting and Data System v. 2, sensitivity, specificity, positive predictive value and negative predictive value was 64%, 94%, 98% and 36%. MP-MRI under staged recurrent cancer in 63%. A modified scoring system in which DCE was used as a co-dominant sequence resulted in improved diagnostic sensitivity (61%-76%) following subgroup analysis.

CONCLUSION

Our results show MP-MRI has moderate sensitivity (64%) and high specificity (94%) in detecting radio-recurrent intraprostatic disease, though disease tends to be under quantified and under staged. Greater emphasis on dynamic contrast images in overall scoring can improve diagnostic sensitivity.

ADVANCES IN KNOWLEDGE

MP-MRI tends to under quantify and under stage radio-recurrent prostate cancer. DCE has a potentially augmented role in detecting recurrent tumour compared with the de novo setting. This has relevance in the event of any future modified MP-MRI scoring system for the irradiated gland.

Prostate Magnetic Resonance Imaging for Local Recurrence Reporting (PI-RR): International Consensus -based Guidelines on Multiparametric Magnetic Resonance Imaging for Prostate Cancer Recurrence after Radiation Therapy and Radical Prostatectomy

BACKGROUND

Imaging techniques are used to identify local recurrence of prostate cancer (PCa) for salvage therapy and to exclude metastases that should be addressed with systemic therapy. For magnetic resonance imaging (MRI), a reduction in the variability of acquisition, interpretation, and reporting is required to detect local PCa recurrence in men with biochemical relapse after local treatment with curative intent.

OBJECTIVE

To propose a standardised method for image acquisition and assessment of PCa local recurrence using MRI after radiation therapy (RP) and radical prostatectomy (RT).

EVIDENCE ACQUISITION

Prostate Imaging for Recurrence Reporting (PI-RR) was formulated using the existing literature. An international panel of experts conducted a nonsystematic review of the literature. The PI-RR system was created via consensus through a combination of face-to-face and online discussions.

EVIDENCE SYNTHESIS

Similar to with PI-RADS, based on the best available evidence and expert opinion, the minimum acceptable MRI parameters for detection of recurrence after radiation therapy and radical prostatectomy are set. Also, a simplified and standardised terminology and content of the reports that use five assessment categories to summarise the suspicion of local recurrence (PI-RR) are designed. PI-RR scores of 1 and 2 are assigned to lesions with a very low and low likelihood of recurrence, respectively. PI-RR 3 is assigned if the presence of recurrence is uncertain. PI-RR 4 and 5 are assigned for a high and very high likelihood of recurrence, respectively. PI-RR is intended to be used in routine clinical practice and to facilitate data collection and outcome monitoring for research.

CONCLUSIONS

This paper provides a structured reporting system (PI-RR) for MRI evaluation of local recurrence of PCa after RT and RP.

PATIENT SUMMARY

A new method called PI-RR was developed to promote standardisation and reduce variations in the acquisition, interpretation, and reporting of magnetic resonance imaging for evaluating local recurrence of prostate cancer and guiding therapy.

Arguments against using an abbreviated or biparametric prostate MRI protocol

Currently there is a lot of interest in the use of a "biparametric" or "abbreviated" prostate MR protocol, which usually refers to removal of the dynamic contrast-enhanced (DCE) MRI, in the detection of clinically significant prostate cancer. In this article we describe the benefits of DCE as part of the PI-RADS lexicon, with particular reference to its role in PI-RADS V2 category 3 peripheral zone lesions. We also discuss the benefits of triplanar T2-weighted images, and finally discuss how a mpMRI protocol is of benefit in prostate cancer staging, in evaluating for local disease recurrence, and as a biomarker for neoadjuvant therapy response.

Roundtable: arguments in support of using multi-parametric prostate MRI protocol

There is increasing evidence to suggest the value of bi-parametric prostate MRI to replace multi-parametric MRI, which includes the dynamic contrast enhancement (DCE) sequence. In this review, we discuss the value of DCE in select scenarios, specifically in resolving equivocal cases, improving the diagnostic accuracy in the inexperienced reader, rescuing exams in the settings of failed T2W and DWI, detecting biochemical recurrence, while imposing minimal to no risk to the patient with respect to IV gadolinium use, specifically group II agents.

Multiparametric MRI as a Biomarker of Response to Neoadjuvant Therapy for Localized Prostate Cancer-A Pilot Study

RATIONALE AND OBJECTIVES

To explore a role for multiparametric MRI (mpMRI) as a biomarker of response to neoadjuvant androgen deprivation therapy (ADT) for prostate cancer (PCa).

MATERIALS AND METHODS

This prospective study was approved by the institutional review board and was HIPAA compliant. Eight patients with localized PCa had a baseline mpMRI, repeated after 6-months of ADT, followed by prostatectomy. mpMRI indices were extracted from tumor and normal regions of interest (TROI/NROI). Residual cancer burden (RCB) was measured on mpMRI and on the prostatectomy specimen. Paired t-tests compared TROI/NROI mpMRI indices and pre/post-treatment TROI mpMRI indices. Spearman's rank tested for correlations between MRI/pathology-based RCB, and between pathological RCB and mpMRI indices.

RESULTS

At baseline, TROI apparent diffusion coefficient (ADC) was lower and dynamic contrast enhanced (DCE) metrics were higher, compared to NROI (ADC: 806 ± 137 × 10^-6 vs. 1277 ± 213 × 10^-6 mm²/sec, p = 0.0005; K^trans: 0.346 ± 0.16 vs. 0.144 ± 0.06 min^-1, p = 0.002; AUC₉₀: 0.213 ± 0.08 vs. 0.11 ± 0.03, p = 0.002). Post-treatment, there was no change in TROI ADC, but a decrease in TROI K^trans (0.346 ± 0.16 to 0.188 ± 0.08 min^-1; p = 0.02) and AUC₉₀ (0.213 ± 0.08 to 0.13 ± 0.06; p = 0.02). Tumor volume decreased with ADT. There was no difference between mpMRI-based and pathology-based RCB, which positively correlated (⍴ = 0.74-0.81, p < 0.05). Pathology-based RCB positively correlated with post-treatment DCE metrics (⍴ = 0.76-0.70, p < 0.05) and negatively with ADC (⍴ = -0.79, p = 0.03).

CONCLUSION

Given the heterogeneity of PCa, an individualized approach to ADT may maximize potential benefit. This pilot study suggests that mpMRI may serve as a biomarker of ADT response and as a surrogate for RCB at prostatectomy.

Post-treatment prostate MRI

Accurate early detection of recurrent prostate cancer after surgical or nonsurgical treatment is increasingly relevant in the era of evolving options for salvage therapy. The importance of differentiating between local tumor recurrence, distant metastatic disease, and a combination of both in a patient with biochemical recurrence of prostate cancer is essential for appropriate treatment selection. Magnetic resonance imaging (MRI) is the best test for localization and characterization of locally residual or recurrent prostate cancer. It is essential for the radiologist involved in prostate MRI interpretation to be familiar with key imaging findings and advantages of different sequences to reach a confident diagnosis in the post-treatment setting. In this pictorial review, we present imaging findings of post-treatment prostate MRI including expected post-treatment anatomy and imaging characteristics, and the typical appearances of local tumor recurrence after radical prostatectomy, radiation therapy, and focal therapy for prostate cancer. While a multi-parametric MRI approach remains key just as in the treatment-naïve gland, this review emphasizes the much greater importance of the dynamic contrast-enhanced MRI sequence for evaluation in the post-treatment setting.

MRI in the Management of Prostate Cancer

Multiparametric MRI has a changing role in prostate cancer diagnosis. Internationally recognized consensus documents such as prostate imaging reporting and data system version have been developed and adapted to standardize the acquisition and reporting of prostate MRI. The improvement in scanning techniques and development of highly sensitive functional sequences have improved the detection of clinically significant prostate cancer as well as treatment planning and follow up. This has led to a recent NICE recommendation to use prostate MRI as the initial investigation in men with clinically suspected localized disease. The results of several recent international MRI prostate trials are influencing the way imaging is used to stratify which patients require a prostate biopsy as well as how MRI guidance is used to target biopsies.

Imaging Biochemical Recurrence After Prostatectomy: Where Are We Headed?

OBJECTIVE. In this article, we discuss the evolving roles of imaging modalities in patients presenting with biochemical recurrence after prostatectomy. CONCLUSION. Multiple imaging modalities are currently available to evaluate patients with prostate cancer presenting with biochemical recurrence after prostatectomy. Multiparametric MRI (mpMRI) focuses on the postsurgical bed as well as regional lymph nodes and bones. PET/CT studies using ¹⁸F-fluciclovine, ¹¹C-choline, and prostate-specific membrane antigen (PSMA) ligands are useful in detecting locoregional and distant metastasis. Multiparametric MRI is preferred for patients with low risk of metastasis for localizing recurrence in prostate bed as well as pelvic lymph node and bone recurrence. Moreover, mpMRI aids in guiding biopsy and additional salvage treatments. For patients with high risk of metastatic disease, both mpMRI and whole-body PET/CT may be performed. PET/MRI using ⁶⁸Ga-PSMA has potential to enable a one-stop shop for local recurrence and metastatic disease evaluation, and clinical trials of PET/MRI are ongoing.

Sensitivity of CE-MRI in detecting local recurrence after radical prostatectomy

AIM

The aim of our study was to evaluate the sensitivity of contrast-enhanced magnetic resonance (CE-MR) with phased array coil in the diagnosis of local recurrence in patients with prostate cancer after radical prostatectomy and referred for salvage radiotherapy (SRT).

MATERIALS AND METHODS

This retrospective study included 73 patients treated with SRT after radical prostatectomy in the period between September 2006 and November 2017. All patients performed a CE-MRI with phased array coil before the start of SRT. A total of 213 patients treated at the ASST Grande Ospedale Metropolitano Niguarda in the period between September 2006 and November 2017 with SRT after radical prostatectomy were reviewed. Seventy-three patients with a CE-MRI with phased array coil of the pelvis before the start of SRT were included in the present study.

RESULTS

At imaging review, recurrence local recurrent disease was diagnosed in 48 of 73 patients. By considering as reference standard the decrease in prostate-specific antigen (PSA) value after radiotherapy, we defined: 41 true positive (patients with MRI evidence of local recurrence and PSA value decreasing after SRT), 7 false positive (patients with MRI evidence of local recurrence without biochemical response after SRT), 3 true negative (patients without MRI evidence of local recurrence and stable or increased PSA value after SRT) and 22 false negative (patients without MRI evidence of local recurrence and PSA value decreasing after SRT) cases. The sensitivity values were calculated in relation to the PSA value before the start of treatment, obtaining a value of 74% for PSA above 0.2 ng/mL.

CONCLUSION

The sensitivity of CE-MRI in local recurrence detection after radical prostatectomy increases with increasing PSA values. CE-MRI with phased array coil can detect local recurrences after radical prostatectomy with a good sensitivity in patients with pre-RT PSA value above 0.2 ng/mL.

Magnetic Resonance Imaging Assessment After Therapy in Prostate Cancer

Prostate cancer is the fifth leading cause of death worldwide. A variety of treatment options is available for localized prostate cancer and may range from active surveillance to focal therapy or whole gland treatment, that is, surgery or radiotherapy. Serum prostate-specific antigen levels are an important tool to monitor treatment success after whole gland treatment, unfortunately prostate-specific antigen is unreliable after focal therapy. Multiparametric magnetic resonance imaging of the prostate is rapidly gaining field in the management of prostate cancer and may play a crucial role in the evaluation of recurrent prostate cancer. This article will focus on postprocedural magnetic resonance imaging after different forms of local therapy in patients with prostate cancer.

Magnetic Resonance-Guided Prostate Ablation

In 2019, the American Cancer Society (ACS) estimates that 174,650 new cases of prostate cancer will be diagnosed and 31,620 will die due to the prostate cancer in the United States. Prostate cancer is often managed with aggressive curative intent standard therapies including radiotherapy or surgery. Regardless of how expertly done, these standard therapies often bring significant risk and morbidity to the patient's quality of life with potential impact on sexual, urinary, and bowel functions. Additionally, improved screening programs, using prostatic-specific antigen and transrectal ultrasound-guided systematic biopsy, have identified increasing numbers of low-risk, low-grade "localized" prostate cancer. The potential, localized, and indolent nature of many prostate cancers presents a difficult decision of when to intervene, especially within the context of the possible comorbidities of aggressive standard treatments. Active surveillance has been increasingly instituted to balance cancer control versus treatment side effects; however, many patients are not comfortable with this option. Although active debate continues on the suitability of either focal or regional therapy for the low- or intermediate-risk prostate cancer patients, no large consensus has been achieved on the adequate management approach. Some of the largest unresolved issues are prostate cancer multifocality, limitations of current biopsy strategies, suboptimal staging by accepted imaging modalities, less than robust prediction models for indolent prostate cancers, and safety and efficiency of the established curative therapies following focal therapy for prostate cancer. In spite of these restrictions, focal therapy continues to confront the current paradigm of therapy for low- and even intermediate-risk disease. It has been proposed that early detection and proper characterization may play a role in preventing the development of metastatic disease. There is level-1 evidence supporting detection and subsequent aggressive treatment of intermediate- and high-risk prostate cancer. Therefore, accurate assessment of cancer risk (i.e., grade and stage) using imaging and targeted biopsy is critical. Advances in prostate imaging with MRI and PET are changing the workup for these patients, and advances in MR-guided biopsy and therapy are propelling prostate treatment solutions forward faster than ever.

Multi-parametric MRI zone-specific diagnostic model performance compared with experienced radiologists for detection of prostate cancer

OBJECTIVES

Compare the performance of zone-specific multi-parametric-MRI (mp-MRI) diagnostic models in prostate cancer detection with experienced radiologists.

METHODS

A single-centre, IRB approved, prospective STARD compliant 3 T MRI test dataset of 203 patients was generated to test validity and generalisability of previously reported 1.5 T mp-MRI diagnostic models. All patients included within the test dataset underwent 3 T mp-MRI, comprising T2, diffusion-weighted and dynamic contrast-enhanced imaging followed by transperineal template ± targeted index lesion biopsy. Separate diagnostic models (transition zone (TZ) and peripheral zone (PZ)) were applied to respective zones. Sensitivity/specificity and the area under the receiver operating characteristic curve (ROC-AUC) were calculated for the two zone-specific models. Two radiologists (A and B) independently Likert scored test 3 T mp-MRI dataset, allowing ROC analysis for each radiologist for each prostate zone.

RESULTS

Diagnostic models applied to the test dataset demonstrated a ROC-AUC = 0.74 (95% CI 0.67-0.81) in the PZ and 0.68 (95% CI 0.61-0.75) in the TZ. Radiologist A/B had a ROC-AUC = 0.78/0.74 in the PZ and 0.69/0.69 in the TZ. Radiologists A and B each scored 51 patients in the PZ and 41 and 45 patients respectively in the TZ as Likert 3. The PZ model demonstrated a ROC-AUC = 0.65/0.67 for the patients Likert scored as indeterminate by radiologist A/B respectively, whereas the TZ model demonstrated a ROC-AUC = 0.74/0.69.

CONCLUSION

Zone-specific mp-MRI diagnostic models demonstrate generalisability between 1.5 and 3 T mp-MRI protocols and show similar classification performance to experienced radiologists for prostate cancer detection. Results also indicate the ability of diagnostic models to classify cases with an indeterminate radiologist score.

KEY POINTS

• MRI diagnostic models had similar performance to experienced radiologists for classification of prostate cancer. • MRI diagnostic models may help radiologists classify tumour in patients with indeterminate Likert 3 scores.

Implementation of a 5-Minute Magnetic Resonance Imaging Screening Protocol for Prostate Cancer in Men With Elevated Prostate-Specific Antigen Before Biopsy

PURPOSE

The aims of this study were to establish a 5-minute magnetic resonance (MR) screening protocol for prostate cancer in men before biopsy and to evaluate effects on Prostate Imaging Reporting and Data System (PI-RADS) V2 scoring in comparison to a conventional, fully diagnostic multiparametric MR imaging (mpMRI) approach.

MATERIALS AND METHODS

Fifty-two patients with elevated prostate-specific antigen levels and without prior biopsy were prospectively included in this institutional review board-approved study. In all patients, an mpMRI protocol according to the PI-RADS recommendations was acquired on a 3 T MRI system. In addition, an accelerated diffusion-weighted imaging sequence was acquired using simultaneous multislice technique (DW-EPISMS). Two readers independently evaluated the images for the presence/absence of prostate cancer according to the PI-RADS criteria and for additional findings. In a first reading session, only the screening protocol consisting of axial T2-weighted and DW-EPISMS images was made available. In a subsequent reading session, the mpMRI protocol was assessed blinded to the results of the first reading, serving as reference standard.

RESULTS

Both readers successfully established a final diagnosis according to the PI-RADS criteria in the screening and mpMRI protocol. Mean lesion size was 1.2 cm in the screening and 1.4 cm in the mpMRI protocol (P = 0.4) with 35% (18/52) of PI-RADS IV/V lesions. Diagnostic performance of the screening protocol was excellent with a sensitivity and specificity of 100% for both readers with no significant differences in comparison to the mpMRI standard (P = 1.0). In 3 patients, suspicious lymph nodes were reported as additional finding, which were equally detectable in the screening and mpMRI protocol.

CONCLUSIONS

A 5-minute MR screening protocol for prostate cancer in men with elevated prostate-specific antigen levels before biopsy is applicable for clinical routine with similar diagnostic performance as the full diagnostic mpMRI approach.

Importance of dynamic contrast enhanced magnetic resonance imaging for targeting biopsy and salvage treatments after prostate cancer recurrence

Purpose

Evaluate T2 weighted MRI (T2W), diffusion weighted imaging (DWI), and dynamic contrast enhanced MRI (DCE-MRI) for determining areas of prostate cancer recurrence to target biopsy or salvage treatment in patients previously treated with I-125 seed brachytherapy.

Material and methods

MRI data from 15 patients, whose primary treatment was I-125 seed brachytherapy and who were subsequently treated with partial gland salvage high-dose-rate brachytherapy were retrospectively analyzed. Two radiologists independently reviewed imaging on two occasions blinded to clinical and biopsy information. At first review, the T2W and DWI sequences were assessed for likely presence of tumor and at second review, the additional DCE-MRI sequence was assessed. Results were recorded and compared on a prostate diagram divided into 12 sectors (quadrants at each of base, mid-gland, and apex) plus seminal vesicles (SV).

Results

Number of patients for whom recurrence was visible was 7/15 for T2W, 6.5/15 for DWI, and 15/15 for DCE-MRI (average of results for the two radiologists). Approximately, half of the sectors identified as showing recurrence were at the anterior base of the prostate.

Conclusions

In prostate cancer patients previously treated with I-125 permanent seed implants, DCE-MRI is superior to T2W and DWI in defining areas of recurrence, and should be used to target biopsy and for treatment planning of focal salvage therapies.

Efficacy of early imaging with 68Ga-PSMA-I&T in the discrimination of pelvic lesions in prostate cancer patients

OBJECTIVE

⁶⁸Ga-PSMA-uptake shows accumulation in the malignant lesions of prostate cancer patients as early as 5min p.i. Studies indicate the value of adding an early image of the pelvis to the imaging protocol of ⁶⁸Ga-PSMA-11 PET/CT scan showed contradictory results. In this study we planned to assess the significance of an additional early imaging in ⁶⁸Ga-PSMA-I&T PET/CT imaging in prostate cancer patients.

MATERIALS AND METHODS

A total of 35 prostate cancer patients referred to ⁶⁸Ga-PSMA-I&T PET/CT imaging for restaging of the disease due to suspicion of relapse after definitive therapy were enrolled. First an early static pelvic image was obtained at a maximum of 300s following injection of the radiotracer. Sixty minutes postinjection a whole-body PET/CT scan was conducted with an emission time of 3min per bed position. The lesions which were categorized as local recurrence, bone lesion and lymph node metástasis in the early images, were compared with the late images in terms of number of lesions detected and SUVmax values.

RESULTS

⁶⁸Ga-PSMA-I&T PET/CT was positive in 23 of 35 patients (65.7%). A pathological uptake was observed in the prostatic bed site, in the pelvic lymph nodes, and in the bones in 17 patients (48.5%), 12 patients (34.2%), and 13 patients (37.1%), respectively. In one patient, focal pathological increased uptake in the prostatic bed with a SUVmax value of 5.8 was detected but this lesion disappeared in the late images. The average SUVmax values of the lesions in the prostatic bed were 13.7±12.1 versus 26.3±23.8 in the 5min and 60min studies respectively (p<0.001). In one patient, the pathological uptake in the lymph node in the early study cleared in the late study, whereas in another accumulation of activity was detected in a pelvic lymph node in the late study, while there was no lymph node detected in the early study. The average SUVmax values of the lymph nodes were 12.1±8.8 versus 26.3±22.6 in the 5min and 60min studies respectively (p<0.001). The average SUVmax values of the bone lesions were 11.4±6.9 versus 15±10.7 in the 5min and 60min studies respectively.

CONCLUSION

Our study is the first in the literature to evaluate the impact of adding an early static pelvic image to the ⁶⁸Ga-PSMA-I&T scan, in the detection rate of the lesions. Although there was no marked discordance between the 2sets of images, the addition of an early image to the imaging protocol of ⁶⁸Ga-PSMA-I&T scan would increase the efficacy of detection of malignant lesions in the pelvis, which might show rapid clearance and has the risk of being masked by the urinary system activity.

Focal Salvage Treatment of Radiorecurrent Prostate Cancer: A Narrative Review of Current Strategies and Future Perspectives

Over the last decades, primary prostate cancer radiotherapy saw improving developments, such as more conformal dose administration and hypofractionated treatment regimens. Still, prostate cancer recurrences after whole-gland radiotherapy remain common, especially in patients with intermediate- to high-risk disease. The vast majority of these patients are treated palliatively with androgen deprivation therapy (ADT), which exposes them to harmful side-effects and is only effective for a limited amount of time. For patients with a localized recurrent tumor and no signs of metastatic disease, local treatment with curative intent seems more rational. However, whole-gland salvage treatments such as salvage radiotherapy or salvage prostatectomy are associated with significant toxicity and are, therefore, uncommonly performed. Treatments that are solely aimed at the recurrent tumor itself, thereby better sparing the surrounding organs at risk, potentially provide a safer salvage treatment option in terms of toxicity. To achieve such tumor-targeted treatment, imaging developments have made it possible to better exclude metastatic disease and accurately discriminate the tumor. Currently, focal salvage treatment is being performed with different modalities, including brachytherapy, cryotherapy, high-intensity focused ultrasound (HIFU), and stereotactic body radiation therapy (SBRT). Oncologic outcomes seem comparable to whole-gland salvage series, but with much lower toxicity rates. In terms of oncologic control, these results will improve further with better understanding of patient selection. Other developments, such as high-field diagnostic MRI and live adaptive MRI-guided radiotherapy, will further improve precision of the treatment.

The Use of Quantitative Imaging in Radiation Oncology: A Quantitative Imaging Network (QIN) Perspective

Modern radiation therapy is delivered with great precision, in part by relying on high-resolution multidimensional anatomic imaging to define targets in space and time. The development of quantitative imaging (QI) modalities capable of monitoring biologic parameters could provide deeper insight into tumor biology and facilitate more personalized clinical decision-making. The Quantitative Imaging Network (QIN) was established by the National Cancer Institute to advance and validate these QI modalities in the context of oncology clinical trials. In particular, the QIN has significant interest in the application of QI to widen the therapeutic window of radiation therapy. QI modalities have great promise in radiation oncology and will help address significant clinical needs, including finer prognostication, more specific target delineation, reduction of normal tissue toxicity, identification of radioresistant disease, and clearer interpretation of treatment response. Patient-specific QI is being incorporated into radiation treatment design in ways such as dose escalation and adaptive replanning, with the intent of improving outcomes while lessening treatment morbidities. This review discusses the current vision of the QIN, current areas of investigation, and how the QIN hopes to enhance the integration of QI into the practice of radiation oncology.

Role of MRI and added value of diffusion-weighted and gadolinium-enhanced MRI for the diagnosis of local recurrence from rectal cancer

PURPOSE

To evaluate whether the addition of gadolinium-enhanced MRI and diffusion-weighted imaging (DWI) improves T2 sequence performance for the diagnosis of local recurrence (LR) from rectal cancer and to assess which approach is better at formulating this diagnosis among readers with different experience.

METHODS

Forty-three patients with suspected LR underwent pelvic MRI with T2 weighted (T2) sequences, gadolinium fat-suppressed T1 weighted sequences (post-contrast T1), and DWI sequences. Three readers (expert: G, intermediate: E, resident: V) scored the likelihood of LR on T2, T2 + post-contrast T1, T2 + DWI, and T2 + post-contrast T1 + DWI.

RESULTS

In total, 18/43 patients had LR; on T2 images, the expert reader achieved an area under the ROC curve (AUC) of 0.916, sensitivity of 88.9%, and specificity of 76%; the intermediate reader achieved values of 0.890, 88.9%, and 48%, respectively, and the resident achieved values of 0.852, 88.9%, and 48%, respectively. DWI significantly improved the AUC value for the expert radiologist by up to 0.999 (p = 0.04), while post-contrast T1 significantly improved the AUC for the resident by up to 0.950 (p = 0.04). For the intermediate reader, both the T2 + DWI AUC and T2 + post-contrast T1 AUC were better than the T2 AUC (0.976 and 0.980, respectively), but with no statistically significant difference. No statistically significant difference was achieved by any of the three readers by comparing either the T2 + DWI AUCs to the T2 + post-contrast T1 AUCs or the AUCs of the two pairs of sequences to those of the combined three sequences. Furthermore, using the T2 sequences alone, all of the readers achieved a fair number of "equivocal" cases: they decreased with the addition of either DWI or post-contrast T1 sequences and, for the two less experienced readers, they decreased even more with the three combined sequences.

CONCLUSIONS

Both DWI and T1 post-contrast MRI increased diagnostic performance for LR diagnosis compared to T2; however, no significant difference was observed by comparing the two different pairs of sequences with the three combined sequences.

MR-Guided Prostate Interventions

Prostate cancer is the most commonly diagnosed noncutaneous cancer and second leading cause of death in men. Many patients with clinically organ-confined prostate cancer undergo definitive treatment of the whole gland, including radical prostatectomy, radiation therapy, and cryosurgery. Active surveillance is a growing alternative option for patients with documented low-volume and low-grade prostate cancer. However, many patients are wanting a less morbid focal treatment alternative. With recent advances in software and hardware of magnetic resonance imaging (MRI), multiparametric MRI of the prostate has been shown to improve the accuracy in detecting and characterizing clinically significant prostate cancer. Targeted biopsy is increasingly utilized to improve the yield of MR detected, clinically significant prostate cancer and to decrease in detection of indolent prostate cancer. MR-guided targeted biopsy techniques include cognitive MR fusion transrectal ultrasound (TRUS) biopsy, in-bore transrectal targeted biopsy using robotic transrectal device, and in-bore direct MR-guided transperineal biopsy with a software based transperineal grid template. In addition, advances in MR-compatible thermal ablation technology allow accurate focal or regional delivery of thermal ablative energy to the biopsy-proved, MRI-detected tumor. MR-guided ablative treatment options include cryoablation, laser ablation, and high-intensity focused ultrasound with real-time or near simultaneous monitoring of the ablation zone. We present a contemporary review of MR-guided techniques for prostatic interventions.

Multiparametric magnetic resonance imaging: Overview of the technique, clinical applications in prostate biopsy and future directions

Multiparametric magnetic resonance imaging (mpMRI) has managed to change the paradigms on prostate cancer detection and risk classification. The most clear-cut indication of mpMRI in guidelines is the patients with a history of negative biopsy/increasing prostate-specific antigen (PSA), and presence of additional findings supporting its use in non biopsied patients and active surveillance. mpMRI complements standard clinical exam, PSA measurements, and systematic biopsy, and will miss some tumors that lack enough size or change in tissue density. Use of mpMRI is likely to increase, and further developments in the technique will be important for safe adoption of focal therapy concepts. Here we present a brief summary about mpMRI and its use in detection, risk classification and follow-up of prostate cancer.

Innovations in imaging modalities for recurrent and metastatic prostate cancer: a systematic review

INTRODUCTION

The last decade has witnessed tremendous changes in the management of advanced and metastatic castration resistant prostate cancer. In the current systematic review, we analyze novel imaging techniques in the setting of recurrent and metastatic prostate cancer (PCa), exploring available data and highlighting future exams which could enter clinical practice in the upcoming years.

EVIDENCE ACQUISITION

The National Library of Medicine Database was searched for relevant articles published between January 2012 and August 2017. A wide search was performed including the combination of following words: "Prostate" AND "Cancer" AND ("Metastatic" OR "Recurrent") AND "imaging" AND ("MRI" OR "PET"). The selection procedure followed the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) principles and is presented using a PRISMA flow chart.

EVIDENCE SYNTHESIS

Novel imaging techniques, as multiparametric magnetic resonance imaging (MRI), whole-body MRI and Choline and prostate-specific membrane antigen (PSMA) PET imaging techniques are currently revolutioning the treatment planning in patients with advanced and metastatic PCa, allowing a better characterization of the disease. Multiparametric MRI performs well in the detection of local recurrences, with sensitivity rates of 67-98% and overall diagnostic accuracy of 83-93%, depending on the type of magnetic field strength (1.5 vs. 3T). Whole body MRI instead shows a high specificity (>95%) for bone metastases. PET imaging, and in particular PSMA PET/CT, showed promising results in the detection of both local and distant recurrences, even for low PSA values (<0.5 ng/mL). Sensitivity varies from 77-98% depending on PSA value and PSA velocity.

CONCLUSIONS

Whole body-MRI, NaF PET, Choline-PET/CT and PSMA PET/CT are flourishing techniques which find great application in the field of recurrent and metastatic PCa, in the effort to reduce treatment of "PSA only" and rather focus our therapies on clinical tumor entities. Standardization is urgently needed to allow adequate comparison of results and diffusion on a large scale.

High postprostatectomy prostate-specific antigen level prior to salvage radiation therapy is not always a bad sign

Although radical prostatectomy is a popular treatment modality for clinically localized prostate cancer, 10-year biochemical recurrence can reach 28%. Before salvage radiation therapy (SRT), prostate-specific antigen (PSA) values alone should be used cautiously in predicting SRT eligibility. A long, slow PSA rise may suggest locally confined disease still amenable to SRT; corresponding imaging to identify potential gross recurrence is useful. Patients with local disease may safely benefit from higher doses of radiation.

Detection of Local Recurrence with 3-Tesla MRI After Radical Prostatectomy: A Useful Method for Radiation Treatment Planning?

BACKGROUND/AIM

Salvage radiotherapy improves biochemical control in patients with recurrence of prostate cancer after prostatectomy. Radiotherapy target volumes of the prostatic fossa are based on empirical data and differ between different guidelines. Localization of recurrence with multiparametric magnetic resonance imaging (MRI) might be a feasible approach to localize recurrent lesions.

PATIENTS AND METHODS

Twenty-one patients with biochemical recurrence after radical prostatectomy were included (median prostate-specific antigen (PSA) =0.17 ng/ml). Multi-parametric MRI was performed using a 3-T MR system.

RESULTS

Lesions were detected in seven patients with a median PSA of 0.86 ng/ml (minimum= 0.31 ng/ml). Patients without detectable recurrence had a median PSA of 0.12 ng/ml. All patients with detectable lesions responded to radiotherapy. Eleven out of 14 patients without detectable recurrence also responded. Plasma flow in suspicious lesions was correlated with PSA level.

CONCLUSION

Detection of recurrence at the prostatic fossa with our approach was possible in a minority of patients with a low PSA level. Clinical relevance of plasma flow in suspicious lesions should be further investigated.

Imaging for the Detection of Locoregional Recurrences in Biochemical Progression After Radical Prostatectomy-A Systematic Review

CONTEXT

Local and regional recurrence after radical prostatectomy (RP) can be treated using salvage radiotherapy (SRT). If the recurrence can be delineated on diagnostic imaging, this could allow for increasingly individualized SRT.

OBJECTIVE

This systematic review aimed at evaluating the evidence regarding the usefulness of positron emission tomography (PET) and magnetic resonance imaging (MRI) in identifying local and regional recurrences, with the aim to further individualize the SRT treatment.

EVIDENCE ACQUISITION

A systematic PubMed/Medline search was conducted in December 2015. Studies included were imaging studies of post-RP patients focusing on local and/or regional recurrence where sensitivity and specificity of MRI or PET were the primary end points. Only studies using biopsy, other histological analysis, and/or treatment follow-up as reference standard were included. Quality Assessment of Diagnostic Accuracy Studies-2 was used to score the study quality. Twenty-five articles were deemed of sufficient quality and included in the review.

EVIDENCE SYNTHESIS

[¹¹C]Acetate had the highest pooled sensitivity (92%), while [¹¹C]choline and [¹⁸F]choline had pooled sensitivities of 71% and 84%, respectively. The PET tracer with highest pooled specificity was [¹¹C]choline (86%). Regarding MRI, MR spectroscopy combined with dynamic contrast enhanced (DCE) MRI showed the highest pooled sensitivity (89%). High pooled sensitivities were also seen using multiparametric MRI (84%), diffusion-weighted MRI combined with T2-weigthed (T2w) imaging (82%), and DCE MRI combined with T2w imaging (82%). These also showed high pooled specificities (85%, 89%, and 92%, respectively).

CONCLUSIONS

Both MRI and PET have adequate sensitivity and specificity for the detection of prostate cancer recurrences post-RP. Multiparametric MRI, using diffusion-weighted and/or DCE imaging, and the choline-labeled tracers showed high pooled sensitivity and specificity, although their ranges were broad.

PATIENT SUMMARY

After reviewing imaging studies of recurrent prostate cancer after prostatectomy, we concluded that choline positron emission tomography and diffusion-weighted magnetic resonance imaging can be proposed as the current standard, with high sensitivity and specificity.

Prospective head-to-head comparison of 11C-choline-PET/MR and 11C-choline-PET/CT for restaging of biochemical recurrent prostate cancer

PURPOSE

Whole-body integrated ¹¹C-choline PET/MR might provide advantages compared to ¹¹C-choline PET/CT for restaging of prostate cancer (PC) due to the high soft-tissue contrast and the use of multiparametric MRI, especially for detection of local recurrence and bone metastases.

MATERIALS AND METHODS

Ninety-four patients with recurrent PC underwent a single-injection/dual-imaging protocol with contrast-enhanced PET/CT followed by fully diagnostic PET/MR. Imaging datasets were read separately by two reader teams (team 1 and 2) assessing the presence of local recurrence, lymph node and bone metastases in predefined regions using a five-point scale. Detection rates were calculated. The diagnostic performance of PET/CT vs. PET/MR was compared using ROC analysis. Inter-observer and inter-modality variability, radiation exposure, and mean imaging time were evaluated. Clinical follow-up, imaging, and/or histopathology served as standard of reference (SOR).

RESULTS

Seventy-five patients qualified for the final image analysis. A total of 188 regions were regarded as positive: local recurrence in 37 patients, 87 regions with lymph node metastases, and 64 regions with bone metastases. Mean detection rate between both readers teams for PET/MR was 84.7% compared to 77.3% for PET/CT (p > 0.05). Local recurrence was identified significantly more often in PET/MR compared to PET/CT by team 1. Lymph node and bone metastases were identified significantly more often in PET/CT compared to PET/MR by both teams. However, this difference was not present in the subgroup of patients with PSA values ≤2 ng/ml. Inter-modality and inter-observer agreement (K > 0.6) was moderate to substantial for nearly all categories. Mean reduction of radiation exposure for PET/MR compared to PET/CT was 79.7% (range, 72.6-86.2%). Mean imaging time for PET/CT was substantially lower (18.4 ± 0.7 min) compared to PET/MR (50.4 ± 7.9 min).

CONCLUSIONS

¹¹C-choline PET/MR is a robust imaging modality for restaging biochemical recurrent PC and interpretations between different readers are consistent. It provides a higher diagnostic value for detecting local recurrence compared to PET/CT with the advantage of substantial dose reduction. Drawbacks of PET/MR are a substantially longer imaging time and a slight inferiority in detecting bone and lymph node metastases in patients with PSA values >2 ng/ml. Thus, we suggest the use of ¹¹C-choline PET/MR especially for patients with low (≤2 ng/ml) PSA values, whereas PET/CT is preferable in the subgroup with higher PSA values.

Diffusion weighted imaging of the prostate-principles, application, and advances

This review article aims to provide an overview on the principles of diffusion-weighted magnetic resonance imaging (DW-MRI) and its applications in the imaging of the prostate. DW-MRI with regards to different applications for prostate cancer (PCa) detection and characterization, local staging as well as for active surveillance (AS) and tumor recurrence after radical prostatectomy (RP) will be discussed. Furthermore, advances in DW-MRI techniques like diffusion kurtosis imaging (DKI) will be presented.

68 Ga-PSMA-PET for radiation treatment planning in prostate cancer recurrences after surgery: Individualized medicine or new standard in salvage treatment

BACKGROUND

⁶⁸ Ga-PSMA-PET imaging is a novel promising diagnostic tool to locate early biochemical failure after radical prostatectomy (RP) in prostate cancer (PC) patients. Exact knowledge of the relapse location may result in changes of the therapy concept aside from changes to the TNM stage. To gain data for this approach, we evaluated PC patients receiving ⁶⁸ Ga-PSMA-PET imaging before salvage radiotherapy (RT).

METHODS AND MATERIALS

In this study, 100 patients with biochemical failure after RP± prior RT who underwent ⁶⁸ Ga-PSMA PET/CT or PET/MRI were evaluated undergoing salvage RT in our department. We analyzed TNM staging changes due to ⁶⁸ Ga-PSMA-PET imaging and its influence on RT planning and treatment.

RESULTS

Uptake indicative for tumor recurrence in ⁶⁸ Ga-PSMA-PET was found in 76% of the patients with biochemical recurrent PC. Median PSA level was 1.0 ng/mL (range 0.12-14.7 ng/mL). Of these, 80% showed no morphological correlate in the corresponding CT or MRI. A 43% of all patients experienced a change in TNM stage due to ⁶⁸ Ga-PSMA-PET imaging. Patients had changes from Tx to rcT+ (28%), 12% from pN0 to rcN1, 1% from pN0/cM0 to rcM1a, and 8% from cM0 to rcM1b. Due to the additional knowledge of ⁶⁸ Ga-PSMA-PET imaging, initial planned RT planning was adapted in 59% of all cases. An additional simultaneous integrated boost (SIB) to the prostate bed or lymph nodes was given to 32% and 63%, respectively. Ten patients received stereotactic body RT (SBRT) to single bone metastases.

CONCLUSION

⁶⁸ Ga-PSMA-PET imaging showed a high clinical impact on staging and RT management in patients with biochemically recurrent PC, even at low serum PSA levels. With 43% changes in staging and 59% in radiotherapy planning ⁶⁸ Ga-PSMA-PET could lead to an indispensable tool in guiding radiation treatment in recurrent PC.

Multiparametric Magnetic Resonance Imaging of Recurrent Prostate Cancer

There is growing consensus that multiparametric magnetic resonance imaging (mpMRI) is an effective modality in the detection of locally recurrent prostate cancer after prostatectomy and radiation therapy. The emergence of magnetic resonance (MR)-guided focal therapies, such as cryoablation, high-intensity focused ultrasound, and laser ablation, have made the use of mpMRI even more important, as the normal anatomy is inevitably altered and the detection of recurrence is made more difficult. The aim of this article is to review the utility of mpMRI in detecting recurrent prostate cancer in patients following radical prostatectomy, radiation therapy, and focal therapy and to discuss expected post-treatment mpMRI findings, the varied appearance of recurrent tumors, and their mimics.