Diagnostic Accuracy of Molecular Imaging Techniques for Detecting Prostate Cancer: A Systematic Review

Molecular imaging modalities show valuable non-invasive techniques capable of precisely and selectively addressing molecular markers associated with prostate cancer (PCa). This systematic review provides an overview of imaging markers utilized in positron emission tomography (PET) methods, specifically focusing on the pathways and mediators involved in PCa. This systematic review aims to evaluate and analyse existing literature on the diagnostic accuracy of molecular imaging techniques for detecting PCa. The PubMed, EBSCO, ScienceDirect, and Web of Science databases were searched, identifying 32 studies that reported molecular imaging modalities for detecting PCa. Numerous imaging modalities and radiotracers were used to detect PCa, including 68Ga-prostate-specific membrane antigen (PSMA) PET/computed tomography (CT), 68Ga-PSMA-11 PET/magnetic resonance imaging (MRI), 18F-PSMA-1007 PET/CT, 18F-DCFPyL PET/MRI, 18F-choline PET/MRI, and 18F-fluoroethylcholine PET/MRI. Across 11 studies, radiolabelled 68Ga-PSMA PET/CT imaging had a pooled sensitivity of 80 (95% confidence interval [CI]: 35-93), specificity of 90 (95% CI: 71-98), and accuracy of 86 (95% CI: 64-96). The PSMA-ligand 68Ga-PET/CT showed good diagnostic performance and appears promising for detecting and staging PCa.

Prostate MRI and PSMA-PET in the Primary Diagnosis of Prostate Cancer

Over the last years, prostate magnetic resonance imaging (MRI) has gained a key role in the primary diagnosis of clinically significant prostate cancer (csPCa). While a negative MRI can avoid unnecessary prostate biopsies and the overdiagnosis of indolent cancers, a positive examination triggers biopsy samples targeted to suspicious imaging findings, thus increasing the diagnosis of csPCa with a sensitivity and negative predictive value of around 90%. The limitations of MRI, including suboptimal positive predictive values, are fueling debate on how to stratify biopsy decisions and management based on patient risk and how to correctly estimate it with clinical and/or imaging findings. In this setting, "next-generation imaging" imaging based on radiolabeled Prostate-Specific Membrane Antigen (PSMA)-Positron Emission Tomography (PET) is expanding its indications both in the setting of primary staging (intermediate-to-high risk patients) and primary diagnosis (e.g., increasing the sensitivity of MRI or acting as a problem-solving tool for indeterminate MRI cases). This review summarizes the current main evidence on the role of prostate MRI and PSMA-PET as tools for the primary diagnosis of csPCa, and the different possible interaction pathways in this setting.

PET/MR Technology: Advancement and Challenges

When this article was written, it coincided with the 11th anniversary of the installation of our PET/MR device in Munich. In fact, this was the first fully integrated device to be in clinical use. During this time, we have observed many interesting behaviors, to put it kindly. However, it is more critical that in this process, our understanding of the system also improved - including the advantages and limitations from a technical, logistical, and medical perspective. The last decade of PET/MRI research has certainly been characterized by most sites looking for a "key application." There were many ideas in this context and before and after the devices became available, some of which were based on the earlier work with integrating data from single devices. These involved validating classical PET methods with MRI (eg, perfusion or oncology diagnostics). More important, however, were the scenarios where intermodal synergies could be expected. In this review, we look back on this decade-long journey, at the challenges overcome and those still to come.

MRI/PET Imaging in elevated PSA and localized prostate cancer: a narrative review

OBJECTIVE

To review the recent milestones in MRI and PET based imaging and evaluate their evolving role in the setting of elevated PSA as well as localized prostate cancer.

BACKGROUND

The importance of multiparametric MRI (mpMRI) and PET based imaging for the diagnosis and staging of prostate cancer cannot be understated. Accurate staging has become another significant milestone with the use of PET scans, particularly with prostate specific radiotracers like 68-Gallium Prostate Specific Membrane Antigen (68Ga-PSMA). Integrated PET/MRI systems are commercially available and can be modulated to evaluate the unique needs of localized as well as recurrent prostate cancer.

METHODS

A literature search was performed using PubMed and Google Scholar using the MeSH compliant and other keywords that included prostate cancer, PSA, mpMRI, PET CT, PET/MRI.

CONCLUSIONS

mpMRI has now established itself as the gold-standard of local prostate imaging and has been incorporated into international guidelines as part of the diagnostic work-up of prostate cancer. PSMA PET/CT has shown superiority over conventional imaging even in staging of localized prostate cancer based on recent randomized control data. Imaging parameters from PET/MRI have been shown to be associated with malignancy, Gleason score and tumour volume. As mpMRI and PSMA PET/CT become more ubiquitous and established; we can anticipate more high-quality data, cost optimization and increasing availability of PET/MRI to be ready for primetime in localized prostate cancer.

Optimized Application of 68Ga-Prostate-Specific Membrane Antigen-617 Whole-Body PET/CT and Pelvic PET/MR in Prostate Cancer Initial Diagnosis and Staging

Purpose: To analyze ⁶⁸Ga-PSMA-617 PET/CT or PET/MR and delayed PET/MR images in patients diagnosed with or suspicion of prostate cancer, and to explore the optimal use of PET/CT and PET/MR for initial diagnosis and staging in prostate cancer.

Methods: Images from conventional scan by ⁶⁸Ga-PSMA whole-body PET/CT or PET/MR followed by delayed pelvic PET/MR were retrospectively analyzed. Prostatic ⁶⁸Ga-PSMA uptake was measured as SUVmax1 (conventional scan 1 h post injection) and SUVmax2 (delayed scan 3 h post injection). Age, PSA levels, and SUVmax were compared between benign and malignant cases. The correlation of SUVmax1 and SUVmax2 was analyzed. Diagnostic performance was evaluated by ROC analysis.

Results: Fifty-six patients with 41 prostate cancers and 15 benign prostate lesions were enrolled. Fifty-three patients had paired conventional and delayed scans. Age, tPSA, fPSA levels, and SUVmax were significantly different between benign and malignant cases. A good correlation was found between SUVmax1 and SUVmax2. There was significant difference between SUVmax1 and SUVmax2 in the malignant group (p = 0.001). SUVmax1 had superior diagnostic performance than SUVmax2, SUVmax difference and PSA levels, with a sensitivity of 85.4%, a specificity of 100% and an AUC of 0.956. A combination of SUVmax1 with nodal and/or distant metastases and MR PI-RADS V2 score had a sensitivity and specificity of 100%. Delayed pelvic PET/MR imaging in 33 patients were found to be redundant because these patients had nodal and/or distant metastases which can be easily detected by PET/CT. PET/MR provided incremental value in 8 patients at early-stage prostate cancer based on precise anatomical localization and changes in lesion signal provided by MR.

Conclusion: Combined ⁶⁸Ga-PSMA whole-body PET/CT and pelvic PET/MR can accurately differentiate benign prostate diseases from prostate cancer and accurately stage prostate cancer. Whole-body PET/CT is sufficient for advanced prostate cancer. Pelvic PET/MR contributes to diagnosis and accurate staging in early prostate cancer. Imaging at about 1 h after injection is sufficient in most patients.

ClinicalTrials.gov: NCT03756077. Registered 27 November 2018—Retrospectively registered, https://clinicaltrials.gov/show/NCT03756077.

Clinical PET/MR

Oncologic imaging has been a major focus of clinical research on PET/MR over the last 10 years. Studies so far have shown that PET/MR with ¹⁸F-Fluorodeoxyglucose (FDG) overall provides a similar accuracy for tumor staging as FDG PET/CT. The effective radiation dose of whole-body FDG PET/MR is more than 50% lower than for FDG PET/CT, making PET/MR particularly attractive for imaging of children. However, the longer acquisition times and higher costs have so far limited broader clinical use of PET/MR technology for whole-body staging. With the currently available technology, PET/MR appears more promising for locoregional staging of diseases for which MR is the anatomical imaging modality of choice. These include brain tumors, head and neck cancers, gynecologic malignancies, and prostate cancer. For instance, PET imaging with ligands of prostate-specific membrane antigen, combined with multi-parametric MR, appears promising for detection of prostate cancer and differentiation from benign prostate pathologies as well as for detection of local recurrences. The combination of functional parameters from MR, such as apparent diffusion coefficients, and molecular parameters from PET, such as receptor densities or metabolic rates, is feasible in clinical studies, but clinical applications for this multimodal and multi-parametric imaging approach still need to be defined.

PET/MRI in prostate cancer: a systematic review and meta-analysis

Aim

In recent years, the clinical availability of scanners for integrated positron emission tomography (PET) and magnetic resonance imaging (MRI) has enabled the practical potential of multimodal, combined metabolic-receptor, anatomical, and functional imaging to be explored. The present systematic review and meta-analysis summarize the diagnostic information provided by PET/MRI in patients with prostate cancer (PCa).

Materials and methods

A literature search was conducted in three different databases. The terms used were “choline” or “prostate-specific membrane antigen - PSMA” AND “prostate cancer” or “prostate” AND “PET/MRI” or “PET MRI” or “PET-MRI” or “positron emission tomography/magnetic resonance imaging.” All relevant records identified were combined, and the full texts were retrieved. Reports were excluded if (1) they did not consider hybrid PET/MRI; or (2) the sample size was < 10 patients; or (3) the raw data were not enough to enable the completion of a 2 × 2 contingency table.

Results

Fifty articles were eligible for systematic review, and 23 for meta-analysis. The pooled data concerned 2104 patients. Initial disease staging was the main indication for PET/MRI in 24 studies. Radiolabeled PSMA was the tracer most frequently used. In primary tumors, the pooled sensitivity for the patient-based analysis was 94.9%. At restaging, the pooled detection rate was 80.9% and was higher for radiolabeled PSMA than for choline (81.8% and 77.3%, respectively).

Conclusions

PET/MRI proved highly sensitive in detecting primary PCa, with a high detection rate for recurrent disease, particularly when radiolabeled PSMA was used.

Electronic supplementary material

The online version of this article (10.1007/s00259-020-05025-0) contains supplementary material, which is available to authorized users.

68Ga-PSMA-11 PET/CT combining ADC value of MRI in the diagnosis of naive prostate cancer: Perspective of radiologist

Ga-PSMA-11 positron emission computed tomography /computed tomography (PET/CT) is more sensitive than magnetic resonance imaging (MRI) in detecting prostate cancer (PCa). We evaluated the value of Ga-PSMA-11 PET/CT with MRI in treatment-naive PCa.This retrospective study was approved by the hospital ethics committee. The MRI and Ga-PSMA-11 PET/CT imaging data of 63 cases of highly suspected PCa were enrolled in this study. The SUVmax and apparent diffusion coefficient (ADC), and their ratio, were assessed as diagnostic markers to distinguish PCa from benign disease.There were 107 prostate lesions detected in 63 cases. Forty cases with 64 malignant primary lesions were confirmed PCa, whereas 23 cases had 43 benign lesions. PSMA-avid lesions correlated with hypointense signal on ADC maps and hyperintense signal on diffusion-weighted imaging. The ADC of PCa was lower than that of benign lesions, and SUVmax and SUVmax/ADC of PCa was higher than that of benign lesions (P < .01). ADC had significant negative correlation with Gleason score (GS) and SUVmax, SUVmax, and SUVmax/ADC positively correlated with GS. From ROC analysis, we established cutoff values of ADC, SUVmax, and SUVmax/ADC at 1.02 × 10mm/s, 11.72, and 12.35, respectively, to differentiate PCa from benign lesions. The sensitivity, specificity, and AUC were 90.6%, 58.1%, and 0.816 for ADC, 67.2%, 97.7%, and 0.905 for SUVmax, and 81.2%, 88.4%, and 0.929 for SUVmax/ADC, respectively.Ga-PSMA-11 PET/CT combined with MRI offers higher diagnostic efficacy in the detection of PCa than either modality alone.

Interim Results of a Prospective Prostate-Specific Membrane Antigen-Directed Focal Stereotactic Reirradiation Trial for Locally Recurrent Prostate Cancer

PURPOSE

To report the feasibility, toxicity, and preliminary outcomes (metabolic and biochemical) of ⁶⁸Ga-prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT)-directed focal prostate reirradiation using linear accelerator (LINAC)-based stereotactic body radiation treatment (SBRT).

METHODS AND MATERIALS

From March 2016 to March 2019, 25 patients were enrolled in a prospective single institution trial (ACTRN12617000035325). Eligibility criteria included patients with biopsy proven isolated prostate recurrence after definitive irradiation, with concordant multiparametric MRI and ⁶⁸Ga-PSMA PET/CT findings, and a prostate-specific antigen of less than 15 ng/mL at the time of recurrence. The study included a sequential dose escalation component with the first 18 patients receiving 36 Gy in 6 fractions on alternate days with subsequent patients receiving 38 Gy in 6 fractions assuming acceptable toxicity.

RESULTS

Median age was 72 years (range, 62-83) with a median time between first radiation treatment and salvage SBRT of 8.3 years (range, 4.5- 13.6). Median prostate-specific antigen at reirradiation was 4.1 (range, 1.1-16.6). The median follow-up was 25 months (range, 13-46). Acute grade 1 and 2 genitourinary (GU) toxicity occurred in 6 (24%) and 1 (4%) men, respectively. Acute grade 1 gastrointestinal (GI) toxicity occurred in 8% with one acute grade 3 GI toxicity (4%) due to a rectal ulcer overlying the hydrogel. Late grade 1 and 2 GU toxicity occurred in 28% and 4%. Late grade 1 GI toxicity occurred in 8% with no grade 2 or greater toxicity. Twenty-four patients have undergone per-protocol 12-month ⁶⁸Ga-PSMA PET/CT, of which 23 (92%) demonstrated a complete metabolic response. Biochemical freedom from failure was 80% at 2 years with 3 out of 4 of the biochemical failures exhibiting recurrent local disease.

CONCLUSIONS

PSMA-directed salvage focal reirradiation to the prostate using linear accelerator-based SBRT is feasible and safe. Toxicity was low, with very favorable short term local and biochemical control in a carefully selected cohort of patients.

68Ga-PSMA PET/MRI for the diagnosis of primary and biochemically recurrent prostate cancer: A meta-analysis

PURPOSE

Our meta-analysis aimed to evaluate the diagnostic performance of ⁶⁸Ga-labelled prostate-specific membrane antigen ligand positron emission tomography/magnetic resonance imaging (⁶⁸Ga-PSMA PET/MRI) in patients with primary and biochemically recurrent prostate cancer (PCa).

METHODS

We searched for relevant articles in PubMed, EMBASE, the Cochrane Library and Web of Science until September 12, 2019. Studies regarding the diagnostic performance of⁶⁸Ga-PSMA PET/MRI in detecting primary PCa and biochemical recurrence (BCR) after definitive treatment were included. The quality of each study was assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool. The pooled sensitivity and specificity of PET/MRI in identifying primary PCa and the pooled detection rate of PET/MRI for BCR were calculated using a random-effects model.

RESULTS

A total of 13 studies with 707 patients were included in the analysis, and the pooled sensitivity and specificity of PET/MRI in detecting primary PCa were 0.83 (95 % CI, 0.73-0.90) and 0.81 (95 % CI, 0.61-0.93), respectively. In the pooled analysis of BCR, the pooled detection rate was 76 % (95 % CI, 72 %-79 %). For four levels of PSA (0-0.2 ng/mL, 0.2-1 ng/mL, 1-2 ng/mL and more than 2 ng/mL), the pooled detection rates were 38 %, 67 %, 74 %, and 95 %, respectively. There was no distinct publication bias, but there was significant study heterogeneity.

CONCLUSIONS

⁶⁸Ga-PSMA PET/MRI is likely an effective imaging method in the diagnosis of primary PCa. In addition, the diagnostic accuracy of ⁶⁸Ga-PSMA PET/MRI in patients with BCR was also high, positively correlating with PSA levels.

Optimum Imaging Strategies for Advanced Prostate Cancer: ASCO Guideline

PURPOSE

Provide evidence- and expert-based recommendations for optimal use of imaging in advanced prostate cancer. Due to increases in research and utilization of novel imaging for advanced prostate cancer, this guideline is intended to outline techniques available and provide recommendations on appropriate use of imaging for specified patient subgroups.

METHODS

An Expert Panel was convened with members from ASCO and the Society of Abdominal Radiology, American College of Radiology, Society of Nuclear Medicine and Molecular Imaging, American Urological Association, American Society for Radiation Oncology, and Society of Urologic Oncology to conduct a systematic review of the literature and develop an evidence-based guideline on the optimal use of imaging for advanced prostate cancer. Representative index cases of various prostate cancer disease states are presented, including suspected high-risk disease, newly diagnosed treatment-naïve metastatic disease, suspected recurrent disease after local treatment, and progressive disease while undergoing systemic treatment. A systematic review of the literature from 2013 to August 2018 identified fully published English-language systematic reviews with or without meta-analyses, reports of rigorously conducted phase III randomized controlled trials that compared ≥ 2 imaging modalities, and noncomparative studies that reported on the efficacy of a single imaging modality.

RESULTS

A total of 35 studies met inclusion criteria and form the evidence base, including 17 systematic reviews with or without meta-analysis and 18 primary research articles.

RECOMMENDATIONS

One or more of these imaging modalities should be used for patients with advanced prostate cancer: conventional imaging (defined as computed tomography [CT], bone scan, and/or prostate magnetic resonance imaging [MRI]) and/or next-generation imaging (NGI), positron emission tomography [PET], PET/CT, PET/MRI, or whole-body MRI) according to the clinical scenario.

Utility of Ga68 prostate-specific membrane antigen positron-emission tomography for pre-operative staging of high-risk prostate cancer in a prospective cohort

INTRODUCTION

To assess the yield of Ga68 PSMA PET/CT added to the conventional staging of high-risk prostate cancer in terms of altered staging and changes to management.

METHODS

Patients with high-risk prostate cancer without metastatic disease on conventional staging referred for Ga68 PSMA PET/CT at Mercy Radiology, Auckland, New Zealand, were prospectively recruited. Conventional staging was double read in a blinded fashion by oncology fellowship-trained radiologists, who were also experienced in PET/CT, followed by interpretation of the PSMA PET/CT by the same radiologists. Confirmation of changes in management decision was obtained from the treating surgeon and multidisciplinary team meeting records. Ethical approval was obtained from the Health and Disability Ethics Committee. All patients gave written informed consent.

RESULTS

A total of 49 patients were scanned. Three who were otherwise eligible for radical prostatectomy elected alternative treatments, leaving 46 patients included for analysis in the study. The addition of PSMA PET/CT was associated with highly statistically significant changes in both staging and management. The stage was changed in 32.6% (95% CI 20.8-47.1%, P < 0.001) patients upstaging in 60% and downstaging in 40%; clinical management in 34.8% (95% CI 22.6-49.3%; P < 0.001), with intramodality change in 25% and intermodality change in 75%. Factors predictive of a change in management with PSMA PET/CT included higher Gleason score and a greater proportion of prostatic cores positive for tumour.

CONCLUSION

The addition of Ga68 PSMA PET/CT to conventional staging in high-risk prostate cancer frequently leads to changes in staging and management.

Comparison of preoperative locoregional Ga-68 PSMA-11 PET-CT and mp-MRI results with postoperative histopathology of prostate cancer

BACKGROUND

Conventional imaging modalities are inadequate to evaluate locoregional extension of prostate cancer (PCa). The aim of the current retrospective study was to investigate the diagnostic efficacy of Gallium-68 prostate-specific membrane antigen-11 (Ga-68 PSMA-11) positron emission tomography/computed tomography (PET/CT) and multiparametric magnetic resonance imaging (mp-MRI) for staging preoperative PCa patients with correlating histopathology.

MATERIALS AND METHODS

Twenty-four patients with histologically proven PCa underwent both Ga-68 PSMA-11 PET/CT and mp-MRI before robot-assisted laparoscopic radical prostatectomy. For each tumor area, correlations with histopathological results were defined for tumor localization, extraprostatic extension (EPE) of the tumor, invasion of seminal vesicle (SVI) and bladder neck invasion (BNI). In patients with regional lymph node (LN) dissection, histopathological results were also correlated with imaging modalities.

RESULTS

Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy for detection of EPE and SVI were higher for mp-MRI than Ga-68 PSMA-11 PET/CT. On the other hand Ga-68 PSMA-11 PET/CT had significant successful results for detection of LN metastases when compared with mp-MRI. But for BNI detection both modalities had same insufficient results. Ga-68 PSMA-11 PET/CT had strong results for appropriate tumor localization in the gland.

CONCLUSION

Ga-68 PSMA PET/CT has superior results for assessing local LN metastases and for intraprostatic tumor localization. Whereas, mp-MRI must be the preferred modality for determining SVI and EPE. But both imaging modalities failed for determining BNI accurately. Both modalities should be used in conjunction with each other for better treatment planning.

Comparison of PET/MRI with multiparametric MRI in diagnosis of primary prostate cancer: A meta-analysis

OBJECTIVE

This meta-analysis aimed to compare the diagnostic performance of positron emission tomography (PET)/MRI using various radiotracers with multiparametric (mp) MRI for detection of primary prostate cancer (PCa).

METHODS

A systematic literature search up to January 2019 was performed to identify studies that evaluated the diagnostic value of PET/MRI and mpMRI for detection of PCa in the same patient cohorts and had sufficient data to construct 2 × 2 contingency tables for true-positive (TP), false-positive (FP), false-negative (FN), and true-negative (TN) results. The quality of each study was assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 tool, and pooled sensitivity (SEN) and specificity (SPE) were calculated. Summary receiver operating characteristic (ROC) curves and area under the curves (AUCs) were used to compare the performances of PET/MRI and mpMRI.

RESULTS

We identified 9 eligible studies that included a total of 353 patients. PET/MRI had a SEN of 0.783 (95% CI, 0.758-0.807) and a SPE of 0.899 (95% CI, 0.879-0.917), and mpMRI had a SEN of 0.603 (95% CI, 0.574-0.631) and a SPE of 0.887 (95% CI, 0.866-0.906). PET/MRI had a higher AUC than mpMRI (0.9311, 95% CI, 0.8990-0.9632 vs. 0.8403, 95% CI, 0.7864-0.8942; P =  0.0036). There was no notable publication bias, but there was medium heterogeneity in outcomes. The meta-regression analysis showed the major potential cause of heterogeneity was the use of region-based rather than lesion-based analysis.

CONCLUSION

PET/MRI has very good diagnostic performance and outperforms mpMRI for the diagnosis of primary PCa.

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.