18F-Fluciclovine PET/MRI for preoperative lymph node staging in high-risk prostate cancer patients

The Impact of Positron Emission Tomography Imaging and Tumor Molecular Profiling on Risk Stratification, Treatment Choice, and Oncological Outcomes of Patients with Primary or Relapsed Prostate Cancer: An International Collaborative Review of the Existing Literature

CONTEXT

The clinical introduction of next-generation imaging methods and molecular biomarkers ("radiogenomics") has revolutionized the field of prostate cancer (PCa). While the clinical validity of these tests has thoroughly been vetted, their clinical utility remains a matter of investigation.

OBJECTIVE

To systematically review the evidence to date on the impact of positron emission tomography (PET) imaging and tissue-based prognostic biomarkers, including Decipher, Prolaris, and Oncotype Dx, on the risk stratification, treatment choice, and oncological outcomes of men with newly diagnosed PCa or those with biochemical failure (BCF).

EVIDENCE ACQUISITION

We performed a quantitative systematic review of the literature using the MEDLINE, EMBASE, and Web of Science databases (2010-2022) following the Preferred Reporting Items for Systematic Reviews and Meta-analyses statement guidelines. The validated Quality Assessment of Diagnostic Accuracy Studies 2 scoring system was used to assess the risk of bias.

EVIDENCE SYNTHESIS

A total of 148 studies (130 on PET and 18 on biomarkers) were included. In the primary PCa setting, prostate-specific membrane antigen (PSMA) PET imaging was not useful in improving T staging, moderately useful in improving N staging, but consistently useful in improving M staging in patients with National Comprehensive Cancer Network (NCCN) unfavorable intermediate- to very-high-risk PCa. Its use led to a management change in 20-30% of patients. However, the effect of these treatment changes on survival outcomes was not clear. Similarly, biomarkers in the pretherapy primary PCa setting increased and decreased the risk, respectively, in 7-30% and 32-36% of NCCN low-risk and 31-65% and 4-15% of NCCN favorable intermediate-risk patients being considered for active surveillance. A change in management was noted in up to 65% of patients, with the change being in line with the molecular risk-based reclassification, but again, the impact of these changes on survival outcomes remained unclear. Notably, in the postsurgical primary PCa setting, biomarker-guided adjuvant radiation therapy (RT) was associated with improved oncological control: Δ↓ 2-yr BCF by 22% (level 2b). In the BCF setting, the data were more mature. PSMA PET was consistently useful in improving disease localization-Δ↑ detection for T, N, and M staging was 13-32%, 19-58%, and 9-29%, respectively. Between 29% and 73% of patients had a change in management. Most importantly, these management changes were associated with improved survival outcomes in three trials: Δ↑ 4-yr disease-free survival by 24.3%, Δ↑ 6-mo metastasis-free survival (MFS) by 46.7%, and Δ↑ androgen deprivation therapy-free survival by 8 mo in patients who received PET-concordant RT (level 1b-2b). Biomarker testing in these patients also appeared to be helpful in risk stratifying and guiding the use of early salvage RT (sRT) and concomitant hormonal therapy. Patients with high-genomic-risk scores benefitted from treatment intensification: Δ↑ 8-yr MFS by 20% with the use of early sRT and Δ↑ 12-yr MFS by 11.2% with the use of hormonal therapy alongside early sRT, while low-genomic-risk score patients did equally well with initial conservative management (level 3).

CONCLUSIONS

Both PSMA PET imaging and tumor molecular profiling provide actionable information in the management of men with primary PCa and those with BCF. Emerging data suggest that radiogenomics-guided treatments translate into direct survival benefits for patients, however, additional prospective data are awaited.

PATIENT SUMMARY

In this review, we evaluated the utility of prostate-specific membrane antigen positron emission tomography and tumor molecular profiling in guiding the care of men with prostate cancer (PCa). We found that these tests augmented risk stratification, altered management, and improved cancer control in men with a new diagnosis of PCa or for those experiencing a relapse.

18 F-sodium fluoride positron emission tomography quantitation of bone metastases in African American and non-African American men with metastatic prostate cancer

BACKGROUND

Bone is the most common site of metastases in men with prostate cancer. The objective of this study was to explore potential racial differences in the distribution of tumor metastases in the axial and appendicular skeleton.

METHODS

We conducted a retrospective review of patients with metastatic prostate cancer to the bone as detected by 18 F-sodium fluoride positron emission tomography/computed tomography (18 F-NaF PET/CT) scans. In addition to describing patients' demographics and clinical characteristics, the metastatic bone lesions, and healthy bone regions were detected and quantified volumetrically using a quantitative imaging platform (TRAQinform IQ, AIQ Solutions).

RESULTS

Forty men met the inclusion criteria with 17 (42%) identifying as African Americans and 23 (58%) identifying as non-African Americans. Most of the patients had axial (skull, ribcage, and spine) disease. The location and the number of lesions in the skeleton of metastatic prostate cancer patients with low disease burden were not different by race.

CONCLUSIONS

In low-disease burden patients with metastatic prostate cancer, there were no overall differences by race in the location and number of lesions in axial or appendicular skeleton. Therefore, given equal access to molecular imaging, African Americans might derive similar benefits. Whether this holds true for patients with a higher disease burden or for other molecular imaging techniques is a topic for further study.

Literature review: Imaging in prostate cancer

Imaging plays an increasingly important role in the detection and characterization of prostate cancer (PC). This review summarizes the key conventional and advanced imaging modalities including multiparametric magnetic resonance imaging (MRI) and positron emission tomography (PET) imaging and tries to instruct clinicians in finding the best image modality depending on the patient`s PC-stage. We aim to give an overview of the different image modalities and their benefits and weaknesses in imaging PC. Emphasis is put on primary prostate cancer detection and staging as well as on recurrent and castration resistant prostate cancer. Results from studies using various imaging techniques are discussed and compared. For the different stages of PC, advantages and disadvantages of the different imaging modalities are discussed. Moreover, this review aims to give an outlook about upcoming, new imaging modalities and how they might be implemented in the future into clinical routine. Imaging patients suffering from PC should aim for exact diagnosis, accurate detection of PC lesions and should mirror the true tumor burden. Imaging should lead to the best patient treatment available in the current PC-stage and should avoid unnecessary therapeutic interventions. New image modalities such as long axial field of view PET/CT with photon-counting CT and radiopharmaceuticals like androgen receptor targeting radiopharmaceuticals open up new possibilities. In conclusion, PC imaging is growing and each image modality is aiming for improvement.

ACR Appropriateness Criteria® Pretreatment Detection, Surveillance, and Staging of Prostate Cancer: 2022 Update

Prostate cancer is second leading cause of death from malignancy after lung cancer in American men. The primary goal during pretreatment evaluation of prostate cancer is disease detection, localization, establishing disease extent (both local and distant), and evaluating aggressiveness, which are the driving factors of patient outcomes such as recurrence and survival. Prostate cancer is typically diagnosed after the recognizing elevated serum prostate-specific antigen level or abnormal digital rectal examination. Tissue diagnosis is obtained by transrectal ultrasound-guided biopsy or MRI-targeted biopsy, commonly with multiparametric MRI without or with intravenous contrast, which has recently been established as standard of care for detecting, localizing, and assessing local extent of prostate cancer. Although bone scintigraphy and CT are still typically used to detect bone and nodal metastases in patients with intermediate- or high-risk prostate cancer, novel advanced imaging modalities including prostatespecific membrane antigen PET/CT and whole-body MRI are being more frequently utilized for this purpose with improved detection rates. The ACR 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.

The Performance of FDA-Approved PET Imaging Agents in the Detection of Prostate Cancer

Positron emission tomography (PET) incorporated with X-ray computed tomography (PET/CT) or magnetic resonance imaging (PET/MRI) is increasingly being used as a diagnostic tool for prostate cancer (PCa). In this review, we describe and evaluate the clinical performance of some Food and Drug Administration (FDA)-approved agents used for visualizing PCa: [¹⁸F]FDG, [¹¹C]choline, [¹⁸F]FACBC, [⁶⁸Ga]Ga-PSMA-11, [¹⁸F]DCFPyL, and [¹⁸F]-NaF. We carried out a comprehensive literature search based on articles published from 1 January 2010 to 1 March 2022. We selected English language articles associated with the discovery, preclinical study, clinical study, and diagnostic performance of the imaging agents for the evaluation. Prostate-specific membrane antigen (PSMA)-targeted imaging agents demonstrated superior diagnostic performance in both primary and recurrent PCa, compared with [¹¹C]choline and [¹⁸F]FACBC, both of which target dividing cells and are used especially in patients with low prostate-specific antigen (PSA) values. When compared to [¹⁸F]-NaF (which is suitable for the detection of bone metastases), PSMA-targeted agents were also capable of detecting lesions in the lymph nodes, soft tissues, and bone. However, a limitation of PSMA-targeted imaging was the heterogeneity of PSMA expression in PCa, and consequently, a combination of two PET tracers was proposed to overcome this obstacle. The preliminary studies indicated that the use of PSMA-targeted scanning is more cost efficient than conventional imaging modalities for high-risk PCa patients. Furthering the development of imaging agents that target PCa-associated receptors and molecules could improve PET-based diagnosis of PCa.

Defining Oligometastatic Disease in the New Era of PSMA-PET Imaging for Primary Staging of Prostate Cancer

Oligometastatic prostate cancer has traditionally been defined in the literature as a limited number of metastatic lesions (either to soft tissue or bone), typically based on findings seen on CT, MRI, and skeletal scintigraphy. Although definitions have varied among research studies, many important clinical trials have documented effective treatments and prognostication in patients with oligometastatic prostate cancer. In current clinical practice, prostate-specific membrane antigen (PSMA)-PET/CT is increasingly utilized for the initial staging of high-risk patients and, in many cases, detecting metastases that would have otherwise been undetected with conventional staging imaging. Thus, patients with presumed localized and/or oligometastatic prostate cancer undergo stage migration based on more novel molecular imaging. As a result, it is challenging to apply the data from the era before widespread PET utilization to current clinical practice and to relate current trials using PSMA-PET/CT for disease detection to older studies using conventional staging imaging alone. This manuscript aims to review the definition of oligometastatic prostate cancer, summarize important studies utilizing both PSMA-PET/CT and conventional anatomic imaging, discuss the concept of stage migration, and discuss current problems and challenges with the current definition of oligometastatic disease.

[18F]-Fluciclovine PET/CT for preoperative nodal staging in high-risk primary prostate cancer: final results of a prospective trial

PURPOSE

The conventional imaging flowchart for prostate cancer (PCa) staging may fail in correctly detecting lymph node metastases (LNM). Pelvic lymph node dissection (PLND) represents the only reliable method, although invasive. A new amino acid PET compound, [18F]-fluciclovine, was recently authorized in suspected PCa recurrence but not yet included in the standard staging work-up of primary PCa. A prospective monocentric study was designed to evaluate [18F]-fluciclovine PET/CT diagnostic performance for preoperative LN staging in primary high-risk PCa.

METHODS

Consecutive patients (pts) with biopsy-proven PCa, standard staging (including [11C]choline PET/CT), eligible for PLND, were enrolled to undergo an investigational [18F]-fluciclovine PET/CT. Nodal uptake higher than surrounding background was reported by at least two readers (blinded to [11C]choline) using a visual 5-point scale (1-2 probably negative; 4-5 probably positive; 3 equivocal); SUVmax, target-to-background (aorta-A; bone marrow-BM) ratios (TBRs), were also calculated. PET results were validated with PLND. [18F]-fluciclovine PET/CT performance using visual score and semi-quantitative indexes was analyzed both per patient and per LN anatomical region, compared to conventional [11C]choline and clinical predictive factors (to note that diagnostic performance of [18F]-fluciclovine was explored for LNM but not examined for intrapelvic or extrapelvic M1 lesions).

RESULTS

Overall, 94 pts underwent [18F]-fluciclovine PET/CT; 72/94 (77%) high-risk pts were included in the final analyses (22 pts excluded: 8 limited PLND; 3 intermediate-risk; 2 treated with radiotherapy; 4 found to be M1; 5 neoadjuvant hormonal therapy). Median LNM risk by Briganti nomogram was 19%. LNM confirmed on histology was 25% (18/72 pts). Overall, 1671 LN were retrieved; 45/1671 (3%) LNM detected. Per pt, median no. of removed LN was 22 (mean 23 ± 10; range 8-51), of LNM was 2 (mean 3 ± 2; range 1-10). Median LNM size was 5 mm (mean 5 ± 2.5; range 2-10). On patient-based analyses (n = 72), diagnostic performance for LNM resulted significant with [18F]-fluciclovine (AUC 0.66, p 0.04; 50% sensitivity, 81% specificity, 47% PPV, 83% NPV, 74% accuracy), but not with [11C]choline (AUC 0.60, p 0.2; 50%, 70%, 36%, 81%, and 65% respectively). Briganti nomogram (OR = 1.03, p = 0.04) and [18F]-fluciclovine visual score (≥ 4) (OR = 4.27, p = 0.02) resulted independent predictors of LNM at multivariable analyses. On region-based semi-quantitative analyses (n = 576), PET/CT performed better using TBR parameters (TBR-A similar to TBR-BM; TBR-A fluciclovine AUC 0.61, p 0.35, vs choline AUC 0.57 p 0.54; TBR-BM fluciclovine AUC 0.61, p 0.36, vs choline AUC 0.58, p 0.52) rather than using absolute LN SUVmax (fluciclovine AUC 0.51, p 0.91, vs choline AUC 0.51, p 0.94). However, in all cases, diagnostic performance was not statistically significant for LNM detection, although slightly in favor of the experimental tracer [18F]-fluciclovine for each parameter. On the contrary, visual interpretation significantly outperformed PET semi-quantitative parameters (choline and fluciclovine: AUC 0.65 and 0.64 respectively; p 0.03) and represents an independent predictive factor of LNM with both tracers, in particular [18F]-fluciclovine (OR = 8.70, p 0.002, vs OR = 3.98, p = 0.03).

CONCLUSION

In high-risk primary PCa, [18F]-fluciclovine demonstrates some advantages compared with [11C]choline but sensitivity for metastatic LN detection is still inadequate compared to PLND. Visual (combined morphological and functional), compared to semi-quantitative assessment, is promising but relies mainly on readers' experience rather than on unquestionable LN avidity.

TRIAL REGISTRATION

EudraCT number: 2014-003,165-15.

Molecular Imaging in Primary Staging of Prostate Cancer Patients: Current Aspects and Future Trends

Accurate primary staging is the cornerstone in all malignancies. Different morphological imaging modalities are employed in the evaluation of prostate cancer (PCa). Regardless of all developments in imaging, invasive histopathologic evaluation is still the standard method for the detection and staging of the primary PCa. Magnetic resonance imaging (MRI) and computed tomography (CT) play crucial roles; however, functional imaging provides additional valuable information, and it is gaining ever-growing acceptance in the management of PCa. Targeted imaging with different radiotracers has remarkably evolved in the past two decades. [111In]In-capromab pendetide scintigraphy was a new approach in the management of PCa. Afterwards, positron emission tomography (PET) tracers such as [11C/18F]choline and [11C]acetate were developed. Nevertheless, none found a role in the primary staging. By introduction of the highly sensitive small molecule prostate-specific membrane antigen (PSMA) PET/CT, as well as recent developments in MRI and hybrid PET/MRI systems, non-invasive staging of PCa is being contemplated. Several studies investigated the role of these sophisticated modalities in the primary staging of PCa, showing promising results. Here, we recapitulate the role of targeted functional imaging. We briefly mention the most popular radiotracers, their diagnostic accuracy in the primary staging of PCa, and impact on patient management.

Applications of PET/MRI in Abdominopelvic Oncology

With PET/MRI, the strengths of PET and MRI are combined to allow simultaneous image acquisition and near-perfect image coregistration. MRI is increasingly being used for staging and restaging of abdominopelvic oncologic lesions, including prostate, hepatobiliary, pancreatic, neuroendocrine, cervical, and rectal cancers. Fluorine 18-fluorodeoxyglucose PET/CT has long been considered a cornerstone of oncologic imaging, and the development of multiple targeted radiotracers has led to increased research on and use of these agents in clinical practice. Thus, simultaneously performed PET/MRI enables the acquisition of complementary imaging information, with distinct advantages over PET/CT and MR image acquisitions. The authors provide an overview of PET/MRI, including descriptions of the major differences between PET/MRI and PET/CT, as well as case examples and treatment protocols for patients with commonly encountered malignancies in the abdomen and pelvis. Online supplemental material is available for this article. ^©RSNA, 2021.

Diagnostic Accuracy of 68Ga-PSMA-11 PET for Pelvic Nodal Metastasis Detection Prior to Radical Prostatectomy and Pelvic Lymph Node Dissection: A Multicenter Prospective Phase 3 Imaging Trial

Importance

The presence of pelvic nodal metastases at radical prostatectomy is associated with biochemical recurrence after prostatectomy.

Objective

To assess the accuracy of prostate-specific membrane antigen (PSMA) 68Ga-PSMA-11 positron emission tomographic (PET) imaging for the detection of pelvic nodal metastases compared with histopathology at time of radical prostatectomy and pelvic lymph node dissection.

Design, Setting, and Participants

This investigator-initiated prospective multicenter single-arm open-label phase 3 imaging trial of diagnostic efficacy enrolled 764 patients with intermediate- to high-risk prostate cancer considered for prostatectomy at University of California, San Francisco and University of California, Los Angeles from December 2015 to December 2019. Data analysis took place from October 2018 to July 2021.

Interventions

Imaging scan with 3 to 7 mCi of 68Ga-PSMA-11 PET.

Main Outcomes and Measures

The primary end point was the sensitivity and specificity for the detection pelvic lymph nodes compared with histopathology on a per-patient basis using nodal region correlation. Each scan was read centrally by 3 blinded independent central readers, and a majority rule was used for analysis.

Results

A total of 764 men (median [interquartile range] age, 69 [63-73] years) underwent 1 68Ga-PSMA-11 PET imaging scan for primary staging, and 277 of 764 (36%) subsequently underwent prostatectomy with lymph node dissection (efficacy analysis cohort). Based on pathology reports, 75 of 277 patients (27%) had pelvic nodal metastasis. Results of 68Ga-PSMA-11 PET were positive in 40 of 277 (14%), 2 of 277 (1%), and 7 of 277 (3%) of patients for pelvic nodal, extrapelvic nodal, and bone metastatic disease. Sensitivity, specificity, positive predictive value, and negative predictive value for pelvic nodal metastases were 0.40 (95% CI, 0.34-0.46), 0.95 (95% CI, 0.92-0.97), 0.75 (95% CI, 0.70-0.80), and 0.81 (95% CI, 0.76-0.85), respectively. Of the 764 patients, 487 (64%) did not undergo prostatectomy, of which 108 were lost to follow-up. Patients with follow-up instead underwent radiotherapy (262 of 379 [69%]), systemic therapy (82 of 379 [22%]), surveillance (16 of 379 [4%]), or other treatments (19 of 379 [5%]).

Conclusions and Relevance

This phase 3 diagnostic efficacy trial found that in men with intermediate- to high-risk prostate cancer who underwent radical prostatectomy and lymph node dissection, the sensitivity and specificity of 68Ga-PSMA-11 PET were 0.40 and 0.95, respectively. This academic collaboration is the largest known to date and formed the foundation of a New Drug Application for 68Ga-PSMA-11.

Trial Registration

ClinicalTrials.gov Identifiers: NCT03368547, NCT02611882, and NCT02919111.

Utility of 18F-Fluciclovine PET/MRI for Staging Newly Diagnosed High-Risk Prostate Cancer and Evaluating Response to Initial Androgen Deprivation Therapy: A Prospective Single-Arm Pilot Study

BACKGROUND. Despite advances in prostate cancer treatment, rates of biochemical recurrence remain high, relating to lack of detection of small-volume metastatic disease using conventional imaging for initial staging. OBJECTIVE. The purpose of this study was to assess the potential use of 18F-fluciclovine PET/MRI for initial staging of high-risk prostate cancer and evaluating response to androgen deprivation therapy (ADT). METHODS. This prospective clinical trial enrolled 14 men with newly diagnosed high-risk prostate cancer and negative or equivocal conventional staging imaging for metastatic disease between January 2018 and February 2019. All patients underwent pretreatment 18F-fluciclovine PET/MRI including multiparametric prostate MRI; 12 underwent 18F-fluciclovine PET/MRI after surgery or between ADT and radiotherapy. Confidence in identification of the primary intraprostatic lesion and nodal metastases was independently rated on a 0-3 Likert scale by three readers with nuclear medicine experience for 18F-fluciclovine PET/MRI and three readers with abdominal imaging experience for MRI alone. Findings scored as 2 or 3 by at least two readers of a given modality were considered positive. A single reader measured SUVmean, SUVmax, and volume of the MRI-defined intraprostatic lesion and SUVmax of suspicious lymph nodes on PET before and after initiation of ADT. Changes in SUV were analyzed using nonparametric Wilcox-on signed-rank tests. RESULTS. The biopsy-proven lesion in the prostate gland was accurately identified in all 14 patients on both MRI and 18F-fluciclovine PET/MRI. Suspected nodal metastases were detected in three patients on MRI and seven patients on 18F-fluciclovine PET/MRI. After ADT, all patients showed decreased activity within the intraprostatic lesion and/or all suspicious lymph nodes. The primary lesion SUVmean was 4.5 ± 1.1 (range, 2.7-6.5) before treatment and 2.4 ± 1.1 (range, 0.0-3.6) after initiation of ADT (p = .008). For suspicious lymph nodes, the pretreatment SUVmax was 5.5 ± 3.7 (range, 2.8-12.7) and the post-treatment SUVmax was 2.8 ± 1.4 (range, 1.4-5.5) (p = .03). CONCLUSION.18F-labeled fluciclovine PET/MRI shows potential utility in initial staging of high-risk prostate cancer and in evaluating response to ADT. CLINICAL IMPACT. Given the FDA approval and widespread availability of 18F-fluciclovine, the findings could have an impact in the immediate future in guiding initial management of patients with prostate cancer. TRIAL REGISTRATION. ClinicalTrials.gov NCT03264456.

PET Imaging for Prostate Cancer

The role of PET imaging with ¹¹C-choline and ¹⁸F-fluciclovine in evaluating patients with prostate cancer (PCa) has become more important over the years and has been incorporated into the NCCN guidelines. A new generation of PET radiotracers targeting the prostate-specific membrane antigen (PSMA) is widely used outside the United States to evaluate patients with primary PCa and PCa recurrence. PET imaging influences treatment planning and demonstrates a significantly higher disease detection rate than conventional imaging such as computed tomography and MR imaging. Early data indicate that using PET radiotracers such as ¹⁸F-fluciclovine and PSMA improves patient outcomes. 68-Ga-PSMA-11 and 18F-DCFPyL-PET/CT were recently approved by the US Food & Drug Administration (FDA) for clinical use. Other PSMA radiotracers, including fluorinated variants, will likely gain FDA approval in the not-too-distant future.

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.

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.

Diagnostic accuracy of 18F-fluciclovine PET/CT in primary lymph node staging of prostate cancer

INTRODUCTION

To determine preoperative diagnostic accuracy of 18F-fluciclovine PET/CT-scan in detection (or exclusion) of lymph node metastases (LNM) in men with prostate cancer (PCa) in comparison to the histopathological results of the extended pelvic lymph node dissection (e-PLND).

METHODS

A retrospective medical records-based cohort study, including 47 men with primary PCa who received 18F-fluciclovine PET/CT and subsequent e-PLND for lymph node staging. Incidence and number of visualized LNM, their locations and diameters on 18F-fluciclovine PET/CT were recorded in comparison to the histopathological results of the e-PLND as reference. Positive predictive value (PPV), negative predictive value (NPV), sensitivity, specificity and diagnostic accuracy of 18F-fluciclovine PET/CT were calculated on the basis of histopathology results after e-PLND.

RESULTS

Forty-seven men were eligible for analysis. Median lymph node yield was 19 (range 10-70). A total of 996 lymph nodes were removed, and 59 metastases were found in 21 cases (45%). Preoperative PET was issued 'positive' in 11 men and in 9 of them (82%) this was histopathologically confirmed resulting in a PPV of 82% (95% CI, 51-96). On the contrary, PET was issued 'negative' in 36 cases, but in 12 of them (33%) metastases were detected in the e-PLND specimen, resulting in an NPV of 67% (95% CI, 50-80). The patient-based sensitivity was 43% (95% CI, 24-64) and the patient-based specificity rate was 92% (95% CI, 75-99), whereas overall diagnostic accuracy was established to be 70% in the present cohort.

CONCLUSION

18F-Fluciclovine PET/CT has a high specificity and positive predicted value for the presence of LNM in men with prostate cancer. However, the sensitivity and NPV seem to be limited to exclude the absence of LNM at a clinically acceptable level. Prospective evaluation is necessary to define patients who may benefit from 18F-fluciclovine PET/CT as a triage test for the indication for e-PLND.

An international expert opinion statement on the utility of PET/MR for imaging of skeletal metastases

BACKGROUND

MR is an important imaging modality for evaluating musculoskeletal malignancies owing to its high soft tissue contrast and its ability to acquire multiparametric information. PET provides quantitative molecular and physiologic information and is a critical tool in the diagnosis and staging of several malignancies. PET/MR, which can take advantage of its constituent modalities, is uniquely suited for evaluating skeletal metastases. We reviewed the current evidence of PET/MR in assessing for skeletal metastases and provided recommendations for its use.

METHODS

We searched for the peer reviewed literature related to the usage of PET/MR in the settings of osseous metastases. In addition, expert opinions, practices, and protocols of major research institutions performing research on PET/MR of skeletal metastases were considered.

RESULTS

Peer-reviewed published literature was included. Nuclear medicine and radiology experts, including those from 13 major PET/MR centers, shared the gained expertise on PET/MR use for evaluating skeletal metastases and contributed to a consensus expert opinion statement. [18F]-FDG and non [18F]-FDG PET/MR may provide key advantages over PET/CT in the evaluation for osseous metastases in several primary malignancies.

CONCLUSION

PET/MR should be considered for staging of malignancies where there is a high likelihood of osseous metastatic disease based on the characteristics of the primary malignancy, hight clinical suspicious and in case, where the presence of osseous metastases will have an impact on patient management. Appropriate choice of tumor-specific radiopharmaceuticals, as well as stringent adherence to PET and MR protocols, should be employed.

18F-Fluciclovine PET for Assessment of Prostate Cancer with Histopathology as Reference Standard: A Systematic Review

The PET tracer ¹⁸F-fluciclovine (Axumin) was recently approved in the United States and Europe for men with suspected prostate cancer recurrence following prior treatment. This article summarizes studies where systematic sector-based histopathology was used as reference standard to assess the diagnostic accuracy of the tracer ¹⁸F-fluciclovine PET in patients with prostate cancer.

18F-Fluciclovine Positron Emission Tomography in Prostate Cancer: A Systematic Review and Diagnostic Meta-Analysis

Background: to explore the diagnostic accuracy of 18F-Fluciclovine positron-emission tomography (PET) in prostate cancer (PCa), considering both primary staging prior to radical therapy, biochemical recurrence, and advanced setting. Methods: A systematic web search through Embase and Medline was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. Studies performed from 2011 to 2020 were evaluated. The terms used were “PET” or “positron emission tomography” or “positron emission tomography/computed tomography” or “PET/CT” or “positron emission tomography-computed tomography” or “PET-CT” and “Fluciclovine” or “FACBC” and “prostatic neoplasms” or “prostate cancer” or “prostate carcinoma”. Only studies reporting about true positive (TP), true negative (TN), false positive (FP) and false negative (FN) findings of 18F-fluciclovine PET were considered eligible. Results: Fifteen out of 283 studies, and 697 patients, were included in the final analysis. The pooled sensitivity for 18F-Fluciclovine PET/CT for diagnosis of primary PCa was 0.83 (95% CI: 0.80–0.86), the specificity of 0.77 (95% CI: 0.74–0.80). The pooled sensitivity for preoperative LN staging was 0.57 (95% CI: 0.39–0.73) and specificity of 0.99 (95% CI: 0.94–1.00). The pooled sensitivity for the overall detection of recurrence in relapsed patients was 0.68 (95% CI: 0.63–0.73), and specificity of 0.68 (95% CI: 0.60–0.75). Conclusion: This meta-analysis showed promising results in term of sensitivity and specificity for 18F-Fluciclovine PET/CT to stage the primary lesion and in the assessment of nodal metastases, and for the detection of PCa locations in the recurrent setting. However, the limited number of studies and the broad heterogeneity in the selected cohorts and in different investigation protocols are limitation affecting the strength of these results.

Influence of pelvic lymph node dissection and node-positive disease on biochemical recurrence, secondary treatment, and survival after radical prostatectomy in men with prostate cancer

BACKGROUND

The benefit of pelvic lymph node dissection (PLND) at radical prostatectomy (RP) remains unclear given the low prevalence of known nodal disease (pN1) and concerns about its therapeutic utility.

OBJECTIVE

To characterize the impact of PLND and secondary treatment on oncologic outcomes.

DESIGN, SETTING, AND PARTICIPANTS

Cohort study of men who underwent primary RP with PLND for prostate cancer (PCa) at our institution since 2003. Men stratified by nodal status.

OUTCOME MEASURES AND STATISTICAL ANALYSIS

Outcomes include biochemical recurrence-free survival (bRFS), overall survival, and PCa-specific mortality (PCSM). Multivariable Cox regression models used for each outcome.

RESULTS AND LIMITATIONS

Of 1,543 men who underwent primary RP, 174 (11%) had pN1 disease. Median follow-up was 34 months (interquartile range, 15-62). Seven-year outcomes were similar whether less than or ≥14 LNs dissected. Among node-positive patients, 29% had undetectable (UDT) prostate-specific antigen (PSA), 11% had UDT PSA + adjuvant therapy, and 60% had detectable PSA, and 7-year bRFS differed (75% for UDT PSA, 90% for UDT + adjuvant therapy, 38% for detectable PSA, p < .01). Survival outcomes did not differ. In multivariable analysis, detectable PSA (vs. UDT, HR 5.2, 95% CI 2.0-13.3) associated with worse bRFS. After salvage treatment, 7-year outcomes did not differ between groups. Study limited by retrospective review.

Incidental Detection of Lung Adenocarcinoma Presenting as an Anterior Mediastinal Mass on 18F-Fluciclovine PET/CT in a Patient With Primary Prostate Cancer

F-fluciclovine is a PET radiotracer approved for detection of recurrent prostate cancer, with utility in other malignancies being investigated. We present the case of a 71-year-old man with high-risk primary prostate cancer (Gleason score 9, prostate-specific antigen 34 ng/mL) and newly diagnosed lung adenocarcinoma. As part of a clinical trial (NCT03081884), preoperative F-fluciclovine PET/CT showed localized abnormal uptake in the prostate gland with extracapsular extension. Additionally, an incidental anterior mediastinal mass measuring 2.2 × 1.8 cm demonstrated abnormal radiotracer uptake. Biopsy of the mediastinal mass confirmed invasive lung adenocarcinoma with solid and acinar patterns and high programmed death 1 ligand expression.

Salvage Pelvic Lymph Node Dissection and Current State of Imaging for Recurrent Prostate Cancer: Does a Standard Exist?

PURPOSE OF REVIEW

We aim to evaluate the efficacy of salvage lymph node dissection (SLND) for nodal recurrent prostate cancer after primary treatment. We also provide a review of the diagnostic performance of next-generation sequencing (next-generation imaging (NGI)) radiotracers in the salvage setting.

RECENT FINDINGS

Most studies evaluating SLND include a heterogeneous population with a small sample size and are retrospective in design. The 5-year clinical recurrence-free and cancer-specific survival following SLND are 26-52% and 57-89%, respectively, among prospective studies. NGI improves accuracy in detecting nodal recurrence compared to conventional CT, with PMSA PET-CT showing the most promise. However, limited studies exist comparing imaging modalities and performance is variable at low PSA values. SLND is a promising treatment option, but more prospective data are needed to determine the ideal surgical candidate and long-term oncologic outcomes. More studies comparing different NGI are needed to determine the best imaging modality in patients who may be candidates for salvage treatment.

Pathologic nodal downstaging in men with clinically involved lymph nodes undergoing radical prostatectomy: Implications for definitive locoregional therapy

A prostate cancer (CaP) patient with nonmetastatic but clinical positive lymph nodes (cN+) represents a difficult clinical scenario. We compare overall survival (OS) between cN+ men that underwent radical prostatectomy (RP) and were found to have negative node status (pN) with those found to have positive nodal status (pN+), and assess predictors of discordant nodal status. We queried the National Cancer Data Base between 2004 and 2015 for patients that were cT1-3 cN+ cM0 CaP treated with RP. Patients with 0 nodes, cT4, or cM1 disease were excluded. We compared groups based on pathologic nodal status: Discordant (cN+ -> pN) & Concordant (cN+ -> pN+). Kaplan Meier estimations were used to compare OS. Logistic regression was used to determine possible predictors of nodal status. We find that of 6470 cN+ patients, 1,367 (21.1%) underwent RP, 866 (13.4%) had confirmed nodal status. Discordant status was found in 159 (18.4%) and concordant staging in 707 (81.6%). Differences exist in PSA at diagnosis (7.3 vs. 11.2), biopsy group, # of nodes examined (7 vs. 10), race, and Charlson index. Discordant staging had longer OS compared to Concordant staging (P = 0.007) and similar OS to a 3:1 matched cohort of high risk localized CaP patients used as reference (P = 0.46). Lower Gleason Score (GG1-3) was associated with an increased likelihood of discordant staging. Clinical nodal staging is associated with a substantial false positive rate. Discordant status had better OS than Concordant status and similar OS to matched patients with localized CaP. Clinical nodal staging may inappropriately lead to noncurative therapy in a substantial number of men with potentially curable disease.

Isolated Intravascular Prostate Carcinoma Recurrence Confirmed With 18F-Fluciclovine PET/CT and MRI

Late recurrence of prostate cancer after remission with prior radical prostatectomy is uncommon. This is a unique case of biochemical recurrence after being in remission for 12 years. The patient presented with swelling of the right lower extremity with pelvic MRI demonstrating an arterially enhancing filling defect in the right common iliac. An F-fluciclovine PET/CT showed corresponding increased intravascular radiotracer activity. Targeted biopsy of the intravascular lesion showed poorly differentiated carcinoma, suggestive of prostate origin. Although MRI evaluation is the mainstay for pelvic evaluation, characterization with F-fluciclovine PET/CT imaging adds high whole-body specificity and diagnostic accuracy.

Three-tiered Subclassification System of High-risk Prostate Cancer in Men Managed With Radical Prostatectomy: Implications for Treatment Decision-making

OBJECTIVE

To inform treatment decisions for patients with high-risk prostate cancer (PCa), we determined rates of adverse pathologic factors and overall survival (OS) among subgroups of high-risk men.

METHODS

Using the National Cancer Database, 89,450 patients with clinical N0M0 unfavorable intermediate-risk, favorable high-risk (cT1c, Gleason 6, prostate-specific antigen [PSA] > 20 ng/mL or cT1c, biopsy Gleason 8, PSA < 10 ng/mL), standard high-risk (all other cT3a, biopsy Gleason ≥ 8, or PSA > 20 ng/mL), or very high-risk (cT3b-T4 or biopsy primary Gleason pattern 5) PCa treated with radical prostatectomy were identified. Rates of adverse pathologic factors (positive surgical margins, T4 disease, or pathologic lymph node involvement) were compared across subgroups.

RESULTS

Patients with unfavorable intermediate-risk (n = 31,381) and favorable high-risk (n = 10,296) disease had similar rates of adverse features (7.6% vs 8.2%, adjusted odds ratio 1.00, 95% confidence interval 0.92-1.08, P= .974). Patients with standard high-risk (n = 30,260) or very high-risk (n = 7513) disease were significantly more likely to have adverse pathologic factors (15.9% and 26.5%, P < .001 for both). Patients with unfavorable intermediate-risk and favorable high-risk disease had similar 5-year OS (95.7% vs 95.1%, adjusted hazard ratio 1.06, 95% confidence interval 0.92-1.21, P = .411) but better OS compared to standard and very high-risk patients (93.4% and 88.1%, respectively; P < .001).

CONCLUSION

Unfavorable intermediate-risk or favorable high-risk PCa patients had low rates of adverse pathologic factors and similar OS. In contrast, standard and very high-risk PCa patients had significantly higher rates of adverse pathologic factors and worse OS. This 3-tiered subclassification of high-risk disease may allow for improved treatment selection among patients considering surgery.

Positron emission tomography (PET) radiotracers for prostate cancer imaging

Imaging plays an increasing role in prostate cancer diagnosis and staging. Accurate staging of prostate cancer is required for optimal treatment planning. In detecting extraprostatic cancer and sites of early recurrence, traditional imaging methods (computed tomography, magnetic resonance imaging, radionuclide bone scan) have suboptimal performance. This leaves a gap between known disease recurrence as indicated by rising prostate-specific antigen and the ability to localize the recurrence on imaging. Novel positron emission tomography (PET) agents including radiolabeled choline, fluciclovine (¹⁸F-FACBC), and agents targeting prostate-specific membrane antigen are being developed and tested to increase diagnostic performance of non-invasive prostate cancer localization. When combined with CT or MRI, these tracers offer a combination of functional information and anatomic localization that is superior to conventional imaging methods. These PET radiotracers have varying mechanisms and excretion patterns affecting their pharmacokinetics and diagnostic performance, which will be reviewed in this article.

Pelvic lymph nodes and pathways of disease spread in male pelvic malignancies

PURPOSE

Accurate nodal staging for male urogenital malignancies has important implications for therapy and prognosis. Male pelvic malignancies, including prostatic, penile, testicular, and bladder cancer, typically metastasize to regional lymph nodes first which is reported by the N-stage. Spread beyond these groups to non-regional nodes is regarded as M-stage disease.

METHODS

In this review, we discuss the typical patterns of male pelvic lymphatic drainage and the tumor-specific regional nodal chains.

RESULTS

The impact of tumor-specific imaging features and the implications of previous treatments on staging are discussed.

CONCLUSIONS

While anatomic imaging, including CT and MRI, is the most widely employed imaging modality at present, newer functional imaging techniques have demonstrated promise in the accurate identification and characterization of nodal metastases.

Fluorine-18-Labeled Fluciclovine PET/CT in Primary and Biochemical Recurrent Prostate Cancer Management

OBJECTIVE. The purpose of this article is to review the utility of ¹⁸F-fluciclovine PET/CT in the evaluation of recurrent prostate cancer. CONCLUSION. Fluorine-18-labeled fluciclovine PET/CT has shown promise in the evaluation of recurrent prostate cancer. Its performance has been superior to that of other imaging modalities. It has had good diagnostic accuracy, especially in the detection of extra-prostatic disease recurrence, and the findings have an impact on treatment planning. Gallium-68-labeled prostate-specific membrane antigen PET/CT has also had excellent performance in the detection of biochemically recurrent prostate cancer with detection rates superior to those of fluciclovine PET/CT.

[18F]Fluciclovine Positron Emission Tomography/Computerized Tomography for Preoperative Staging in Patients with Intermediate to High Risk Primary Prostate Cancer

PURPOSE

Accurate preoperative staging of prostate cancer is essential for treatment planning. Conventional imaging is limited in detection of metastases. Our primary aim was to determine if [¹⁸F]fluciclovine positron emission tomography/computerized tomography is an early indicator of subclinical metastasis among patients with high risk prostate cancer.

MATERIALS AND METHODS

A total of 68 patients with unfavorable intermediate to very high risk prostate cancer without systemic disease on conventional imaging were recruited before robotic radical prostatectomy with extended pelvic lymph node dissection. Diagnostic performance of [¹⁸F]fluciclovine positron emission tomography/computerized tomography and conventional imaging for detection of metastatic disease, and correlation of positivity to node and metastatic deposit size were determined.

RESULTS

Overall 57 of 68 patients completed the protocol, of whom 31 had nodal metastasis on histology. [¹⁸F]Fluciclovine positron emission tomography/computerized tomography sensitivity and specificity in detecting nodal metastasis was 55.3% and 84.8% per patient, and 54.8% and 96.4% per region (right and left pelvis, presacral and nonregional), respectively. Compared with conventional imaging [¹⁸F]Fluciclovine positron emission tomography/computerized tomography had significantly higher sensitivity on patient based (55.3% vs 33.3%, p <0.01) and region based (54.8% vs 19.4%, p <0.01) analysis, detecting metastasis in 7 more patients and 22 more regions, with similar high specificity. Four additional patients had distant disease or other cancer detected on [¹⁸F] fluciclovine positron emission tomography/computerized tomography which precluded surgery. Detection of metastasis was related to size of metastatic deposits within lymph nodes and overall metastatic burden.

CONCLUSIONS

[¹⁸F]Fluciclovine positron emission tomography/computerized tomography detects occult metastases not identified on conventional imaging and may help guide treatment decisions and lymph node dissection due to high specificity for metastatic disease.

Diagnostic Performance of PET/CT Using 18F-FACBC in Prostate Cancer: A Meta-Analysis

Background: Diagnostic performance of PET/CT using 18F-fluciclovine (18F-FACBC) in patients with prostate cancer (PCa) has been evaluated in only a few studies. There is no consensus on the diagnostic value of 18F-FACBC PET/CT in PCa recurrence or metastasis (except for bone metastasis), the primary diagnosis of the lesion. Hence, a meta-analysis was conducted to evaluate the performance of 18F-FACBC PET/CT. Methods: The literature published from June 2015 to June 2019 on using 18F-FACBC PET/CT for the diagnosis of PCa was retrieved from PubMed and EMBASE. Pooled sensitivity (Sen), specificity (Spe), positive and negative likelihood ratios (LR+ and LR-), area under the curve (AUC), and diagnostic odds ratio (DOR) of 18F-FACBC PET/CT in patients with PCa were calculated. An SROC map was made, and a meta-regression analysis was carried out. A Fagan plot and likelihood ratio dot plot were drawn. Sensitivity and funnel plot analysis were made. Meta-disc, Review Manager 5.3, and STATA 13 were used for the meta-analysis. Results: A total of nine articles met the strict criteria for diagnostic meta-analysis, which included 363 patients and 345 lesions. Pooled Sen, Spe, LR+, LR-, DOR were 0.88, 0.73, 3.3, 0.17, and 20, respectively. Lesions detected on the PET/CT image included primary lesions and metastases. For the lesion, the doctors considered the abnormal part as a lesion on the PET/CT image by their own experience and expertise, including primary lesions and metastases. For the patient, patients who participated in the trial can be diagnosed as PCa through 18F-FACBC. Conclusion: This study comprehensively evaluated the diagnostic value of 18F-FACBC PET/CT on PCa. Our analysis suggests that 18F-FACBC PET/CT is a valuable agent in diagnosing PCa. More studies are needed for further validation.

Ferumoxytol-Enhanced MR Lymphography for Detection of Metastatic Lymph Nodes in Genitourinary Malignancies: A Prospective Study

OBJECTIVE. The objective of our study was to evaluate the utility of ferumoxytol-enhanced MR lymphography (MRL) in detection of metastatic lymph nodes (LNs) in patients with prostate, bladder, and kidney cancer. SUBJECTS AND METHODS. This phase 2 single-institution study enrolled patients with confirmed prostate (arm 1), bladder (arm 2), and kidney (arm 3) cancer and evidence of suspected LN involvement. Participants underwent ferumoxytol-enhanced MRL 24 and 48 hours after IV injection of 7.5 mg Fe/kg of ferumoxytol. A retrospective quantitative analysis was performed to determine the optimal timing for ferumoxytol-enhanced MRL using percentage change in normalized signal intensity (SI) from baseline to 24 and 48 hours after injection, which were estimated using the linear mixed-effects model in which time (24 vs 48 hours), diseases status, and time and disease status interaction were the fixed-effects independent variables. Differences in normalized SI values between subgroups of lesions were estimated by forming fixed-effects contrasts and tested by the Wald test. RESULTS. Thirty-nine patients (n = 30, arm 1; n = 6, arm 2; n = 3, arm 3) (median age, 65 years) with 145 LNs (metastatic, n = 100; benign, n = 45) were included. LN-based sensitivity, specificity, positive predictive value, and negative predictive value of ferumoxytol-enhanced MRL was 98.0%, 64.4%, 86.0%, and 93.5%, respectively. Sensitivity and specificity of ferumoxytol-enhanced MRL did not vary by LN size. Metastatic LNs showed a significantly higher percentage decrease of normalized SI on MRL at 24 hours after ferumoxytol injection than at 48 hours after ferumoxytol injection (p = 0.023), whereas the normalized SI values for nonmetastatic LNs were similar at both imaging time points (p = 0.260). CONCLUSION. Ferumoxytol-enhanced MRL shows high sensitivity in the detection of metastatic LNs in genitourinary cancers independent of LN size. The SI difference between benign and malignant LNs on ferumoxytol-enhanced MRL appears similar 24 and 48 hours after ferumoxytol injection, suggesting that imaging can be performed safely within 1 or 2 days of injection. Although ferumoxytol-enhanced MRL can be useful in settings without an available targeted PET agent, issues of iron overload and repeatability of ferumoxytol-enhanced MRL remain concerns for this method.

18F-Facbc in Prostate Cancer: A Systematic Review and Meta-Analysis

Trans-1-amino-3-¹⁸F-fluorocyclobutanecarboxylic-acid (anti-[¹⁸F]-FACBC) has been approved for the detection of prostate cancer (PCa) in patients with elevated prostate-specific-antigen following prior treatment. This review and meta-analysis aimed to investigate the diagnostic performance of ¹⁸F-FACBC positron emission tomography/computed-tomography (PET/CT) in the detection of primary/recurrent PCa. A bibliographic search was performed including several databases, using the following terms: "FACBC"/"fluciclovine" AND "prostate cancer"/"prostate" AND "PET"/"Positron Emission Tomography". Fifteen and 9 studies were included in the systematic reviews and meta-analysis, respectively. At patient-based analysis, the pooled sensitivity and specificity of ¹⁸F-FACBC-PET/CT for the assessment of PCa were 86.3% and 75.9%, respectively. The pooled diagnostic odds-ratio value was 16.453, with heterogeneity of 30%. At the regional-based-analysis, the pooled sensitivity of ¹⁸F-FACBC-PET/CT for the evaluation of primary/recurrent disease in the prostatic bed was higher than in the extra-prostatic regions (90.4% vs. 76.5%, respectively); conversely, the pooled specificity was higher for the evaluation of extra-prostatic region than the prostatic bed (89% vs. 45%, respectively). ¹⁸F-FACBC-PET/CT seems to be promising in recurrent PCa, particularly for the evaluation of the prostatic bed. Additional studies to evaluate its utility in clinical routine are mandatory.

Multimodality Imaging of Prostate Cancer

Prostate cancer is a very heterogeneous disease, and contemporary management is focused on identification and treatment of the prognostically adverse high-risk tumors while minimizing overtreatment of indolent, low-risk tumors. In recent years, imaging has gained increasing importance in the detection, staging, posttreatment assessment, and detection of recurrence of prostate cancer. Several imaging modalities including conventional and functional methods are used in different clinical scenarios with their very own advantages and limitations. This continuing medical education article provides an overview of available imaging modalities currently in use for prostate cancer followed by a more specific section on the value of these different imaging modalities in distinct clinical scenarios, ranging from initial diagnosis to advanced, metastatic castration-resistant prostate cancer. In addition to established imaging indications, we will highlight some potential future applications of contemporary imaging modalities in prostate cancer.

The role of 18F-fluciclovine PET in the management of prostate cancer: a systematic review and meta-analysis

AIM

To investigate the diagnostic performance of ¹⁸F-fluciclovine positron-emission tomography (PET) or combined PET and computed tomography (PET/CT) for diagnosis of primary cancer, preoperative lymph node (LN) staging, and detection of recurrent disease of prostate cancer (PCa) through a systematic review and meta-analysis.

MATERIALS AND METHODS

The PubMed and EMBASE databases were searched from the earliest available date of indexing through 31 December 2018, for studies evaluating the diagnostic performance of ¹⁸F-fluciclovine PET or PET/CT for the management of PCa patients. The sensitivities, specificities, and positive and negative likelihood ratios (LR+ and LR-) across the studies were calculated and summary receiver operating characteristic curves were constructed.

RESULTS

Across 13 studies (563 patients), the pooled sensitivity for ¹⁸F-fluciclovine PET or PET/CT for diagnosis of primary PCa was 0.87 (95% confidence interval [CI]: 0.77-0.93) and a pooled specificity of 0.84 (95% CI: 0.68-0.93). For LN staging, the pooled sensitivity was 0.56 (95% CI: 0.37-0.74) and a pooled specificity of 0.98 (95% CI: 0.88-1.00). For detection of recurrent disease, the pooled sensitivity was 0.79 (95% CI: 0.60-0.91) and a pooled specificity of 0.69 (95% CI: 0.59-0.77). In meta-regression analysis, no definite variable was the source of the study heterogeneity.

CONCLUSION

The current meta-analysis showed the moderate sensitivity and specificity of ¹⁸F-fluciclovine PET or PET/CT for the diagnosis of primary cancer, preoperative LN staging, and detection of recurrent PCa. Further large multicentre studies will be necessary to substantiate the diagnostic accuracy of ¹⁸F-fluciclovine PET/CT for management of PCa patients.

Feasibility of Dose Escalating [18F]fluciclovine Positron Emission Tomography Positive Pelvic Lymph Nodes During Moderately Hypofractionated Radiation Therapy for High-Risk Prostate Cancer

Purpose

The aim of this study was to report the treatment planning feasibility of dose escalation to suspicious lymph nodes (LNs) for a series of men who underwent pretreatment [¹⁸F]fluciclovine positron emission tomography (PET)/magnetic resonance imaging (MRI).

Methods and Materials

Cases of men with prostate cancer who enrolled in a clinical trial of pretreatment [¹⁸F]fluciclovine PET who had suspicious LNs were selected. Pelvic LNs <1 cm were defined as positive based on [¹⁸F]fluciclovine-PET if their maximum standardized uptake value (SUV_max) was ≥1.3-fold greater than the reference blood pool SUV_mean, and LNs ≥1 cm were defined as positive if the SUV was greater than the reference SUV bone marrow reference. For each case, a radiation treatment plan was generated to deliver 70 Gy to the prostate and proximal seminal vesicles, 60.2 Gy to the PET-positive LNs, and 50.4 Gy to the elective nodal regions, simultaneously in 28 fractions of 2.5 Gy, 2.15 Gy, and 1.8 Gy, respectively. Treatment planning goals were defined a priori. The resulting target volume and organ-at-risk dosimetry were compared with the original treatment plan.

Results

Four cases were identified, with between 1 and 5 [¹⁸F]fluciclovine PET–positive LNs each. Goals for the prostate and elective nodal target volumes were successfully met in all cases. The goal of covering more than 90% of the positive LN planning target volume by the prescription dose of 60.2 Gy was met in 3 of the 4 cases. This goal was not met in 1 case, but 100% of clinical target volume was covered by 60.2 Gy. The primary organ-at-risk tradeoff was that a small volume (0.5-8.2 cm³) of small bowel would receive ≥54 Gy in each case.

Conclusions

These preliminary results suggest that [¹⁸F]fluciclovine PET/MRI directed dose escalation of suspicious pelvic LNs is likely feasible in the setting of definitive radiation therapy. The potential clinical benefit of dose escalating [¹⁸F]fluciclovine PET–positive LNs should be investigated in a prospective clinical trial.

Circulating Tumor Cells as a Predictor of Treatment Response in Clinically Localized Prostate Cancer

PURPOSE

Using nonenrichment-based, potentially more sensitive Epic Sciences circulating tumor cell (CTC) platform, we sought to detect and characterize CTCs in untreated, high-risk localized prostate cancer and to evaluate their clinical implication.

METHODS

Between 2012 and 2015, blood samples were prospectively collected from patients with National Comprehensive Cancer Network high-risk localized prostate cancer undergoing either radiotherapy (XRT) plus androgen deprivation therapy or radical prostatectomy (RP) with curative intent. Samples were analyzed with the Epic Sciences platform with 4^J,6-diamidino-2-phenylindole, CD45, cytokeratin (CK), and androgen receptor (AR) N-terminal staining. CTC counts were correlated with biochemical recurrence (BCR).

RESULTS

A diversity of CTC subtypes, including CK-positive, CK-negative, AR-positive, and CTC clusters, were observed in 73.3% (33 of 45) of patients with evaluable data. The median follow-up was 14.2 months (range, 0.5 to 43.7 months). BCR occurred more frequently in the RP group than XRT (15 of 26 v one of 19), with most patients in the XRT group continuing to receive androgen deprivation therapy. A higher proportion of metastatic events were observed in the RP group (five of 26 v one of 19). In the RP group, BCR and development of metastases were associated with a higher total number of CTCs, AR-positive CTCs, and CTC phenotypic heterogeneity. One patient who developed BCR and metastases quickly after RP had diverse phenotypical CTC subtypes, and single-cell genomic analyses of all detectable CTCs confirmed common prostate cancer copy number alterations and PTEN loss.

CONCLUSION

CTCs can be identified in most patients with high-risk localized prostate cancer before definitive therapy using the Epic Sciences platform. If confirmed in a larger cohort with longer follow-up, phenotypic and genomic characterization of CTCs pretherapy may provide an additional means of risk stratifying patients with newly diagnosed high-risk disease and potentially help identify patients who could require multimodal therapy.

Diagnostic Performance of 68Gallium Labelled Prostate-Specific Membrane Antigen Positron Emission Tomography/Computed Tomography and Magnetic Resonance Imaging for Staging the Prostate Cancer with Intermediate or High Risk Prior to Radical Prostatectomy: A Systematic Review and Meta-analysis

Purpose

To compare the diagnostic efficiency of ⁶⁸Gallium labelled prostate-specific membrane antigen positron emission tomography (⁶⁸Ga-PSMA PET) and magnetic resonance imaging (MRI) for staging the lymph node metastases (LNMs) in the prostate cancer.

Materials and Methods

A broad search of scientific databases including PubMed, EMBASE, Web of Science, Cochrane Database, and Chinese Biomedicine Literature Database (updated prior to November 1st, 2018) was conducted systematically by two reviewers. In this paper, we evaluated the methodological quality of each included article independently and performed a systematic review and meta-analysis to reveal the summary of the diagnostic performance of ⁶⁸Ga-PSMA PET and MRI in properly identifying LNMs of intermediate- and/or high-risk prostate cancer.

Results

Thirteen eligible articles comprising 1,597 patients were included. For LNMs detection, the pooled sensitivity and specificity of ⁶⁸Ga-PSMA PET were 0.65 (95% confidence interval [CI]: 0.49–0.79) and 0.94 (95% CI: 0.88–0.97), respectively, while the corresponding values of MRI were 0.41 (95% CI: 0.26–0.57) and 0.92 (95% CI: 0.86–0.95). The area under the symmetric receiver-operating characteristic (SROC) curve for ⁶⁸Ga-PSMA PET and MRI were 0.92 and 0.83, respectively.

Conclusions

In intermediate- or high-risk pre-treatment prostate cancer, ⁶⁸Ga-PSMA PET had a higher sensitivity and a slightly different specificity in probing the LNMs when comparing with MRI. Moreover, the area under the SROC curve indicated that ⁶⁸Ga-PSMA PET was a more effective weapon for predicting the LNMs prior to radical surgery.

Rise in Node-Positive Prostate Cancer Incidence in Context of Evolving Use and Extent of Pelvic Lymphadenectomy

BACKGROUND

The incidence of node-positive prostate cancer has risen and might be partially explained by evolving use of lymphadenectomy at a population level. We assessed trends of node-positive prostate cancer in context of extent of lymphadenectomy among men treated surgically for prostate cancer.

PATIENTS AND METHODS

This was a retrospective study using data from a population-based cancer registry to identify men older than 50 years of age diagnosed with prostate cancer from 2010 to 2015 without distant metastases. We considered extent of node dissection as ordinal (1-4, 5-9, 10-14, 15-19, ≥20) and dichotomous (1-14, ≥15) variables. We fit multivariable models to assess trends in receipt of extended lymphadenectomy and then estimated odds of node-positive cancer on the basis of extent of lymphadenectomy.

RESULTS

We identified 280,156 men diagnosed from 2010 to 2015; 5355 men (1.9%) had positive lymph nodes. Incidence of positive nodes increased from 6.4 to 8.4 cases per 100,000 men from 2010 to 2015 (standardized rate ratio, 1.31; 95% confidence interval [CI], 1.20-1.44). Compared with 2010, prostatectomy patients with high-risk (odds ratio [OR], 1.66; 95% CI, 1.42-1.95) and intermediate-risk tumors (OR, 1.66; 95% CI, 1.47-1.88) were more likely to undergo extended lymphadenectomy in 2015. Among high-risk patients, men with ≥20 nodes removed were 7 times more likely to have positive nodes, versus <5 removed (6.1% for 1-4 vs. 32.4% for ≥20; OR, 7.32; 95% CI, 6.16-8.71). After adjusting for extent of dissection, odds of node-positive disease did not increase between 2010 and 2015 (OR, 1.17; 95% CI, 0.98-1.39) among high-risk patients.

CONCLUSION

Increased incidence of node-positive prostate cancer in the United States is partially explained by more frequent use of extended lymphadenectomy.

Simultaneous 18F-fluciclovine Positron Emission Tomography and Magnetic Resonance Spectroscopic Imaging of Prostate Cancer

Purpose: To investigate the associations of metabolite levels derived from magnetic resonance spectroscopic imaging (MRSI) and ¹⁸F-fluciclovine positron emission tomography (PET) with prostate tissue characteristics.

Methods: In a cohort of 19 high-risk prostate cancer patients that underwent simultaneous PET/MRI, we evaluated the diagnostic performance of MRSI and PET for discrimination of aggressive cancer lesions from healthy tissue and benign lesions. Data analysis comprised calculations of correlations of mean standardized uptake values (SUV_mean), maximum SUV (SUV_max), and the MRSI-derived ratio of (total choline + spermine + creatine) to citrate (CSC/C). Whole-mount histopathology was used as gold standard.

Results: The results showed a moderate significant correlation between both SUVmean and SUVmax with CSC/C ratio.

Conclusions: We demonstrated that the simultaneous acquisition of ¹⁸F-fluciclovine PET and MRSI with an integrated PET/MRI system is feasible and a combination of these imaging modalities has potential to improve the diagnostic sensitivity and specificity of prostate cancer lesions.

Imaging as a Personalized Biomarker for Prostate Cancer Risk Stratification

Biomarkers provide objective data to guide clinicians in disease management. Prostate-specific antigen serves as a biomarker for screening of prostate cancer but has come under scrutiny for detection of clinically indolent disease. Multiple imaging techniques demonstrate promising results for diagnosing, staging, and determining definitive management of prostate cancer. One such modality, multiparametric magnetic resonance imaging (mpMRI), detects more clinically significant disease while missing lower volume and clinically insignificant disease. It also provides valuable information regarding tumor characteristics such as location and extraprostatic extension to guide surgical planning. Information from mpMRI may also help patients avoid unnecessary biopsies in the future. It can also be incorporated into targeted biopsies as well as following patients on active surveillance. Other novel techniques have also been developed to detect metastatic disease with advantages over traditional computer tomography and magnetic resonance imaging, which primarily rely on defined size criteria. These new techniques take advantage of underlying biological changes in prostate cancer tissue to identify metastatic disease. The purpose of this review is to present literature on imaging as a personalized biomarker for prostate cancer risk stratification.

Multimodal imaging for radiation therapy planning in patients with primary prostate cancer

Implementation of advanced imaging techniques like multiparametric magnetic resonance imaging (mpMRI) or Positron Emission Tomography (PET) in radiation therapy (RT) planning of patients with primary prostate cancer demands several preconditions: accurate staging of the extraprostatic and intraprostatic tumor mass, robust delineation of the intraprostatic gross tumor volume (GTV) and a reproducible characterization of the prostate cancer's biological properties. In the current review we searched for the currently available imaging techniques and we discussed their ability to fulfill these preconditions. We found that current pretreatment imaging was mainly performed with mpMRI and/or Prostate-specific membrane antigen PET imaging. Both techniques offered an accurate detection of the extraprostatic and intraprostatic tumor burden and had a major impact on RT concepts. However, some studies postulated that mpMRI and PSMA PET had complementary information for intraprostatic GTV detection. Moreover, interobserver differences for intraprostatic tumor delineation based on mpMRI were observed. It is currently unclear whether PET based GTV delineation underlies also interobserver heterogeneity. Further research is warranted to answer whether multimodal imaging is able to visualize biological processes related to prostate cancer pathophysiology and radiation resistance.

Editorial Comment: Advances in MRI and PET of the prostate: concurrence or complementarity?

This Editorial Comment refers to the articles "Diagnostic evaluation of magnetization transfer and diffusion kurtosis imaging for prostate cancer detection in a re-biopsy population" by Barrett T et al., Eur Radiol. 2017 Dec 8 and "18F-Fluciclovine PET/MRI for preoperative lymph node staging in high-risk prostate cancer patients" by Selnæs KM et al., Eur Radiol. 2018 Jan 2.

The Effect of Including Bone in Dixon-Based Attenuation Correction for 18F-Fluciclovine PET/MRI of Prostate Cancer

The objective of this study was to evaluate the effect of including bone in Dixon-based attenuation correction for ¹⁸F-fluciclovine PET/MRI of primary and recurrent prostate cancer. Methods: ¹⁸F-fluciclovine PET data from 2 PET/MRI studies-one for staging of high-risk prostate cancer (28 patients) and one for diagnosis of recurrent prostate cancer (81 patients)-were reconstructed with a 4-compartment (reference) and 5-compartment attenuation map. In the latter, continuous linear attenuation coefficients for bone were included by coregistration with an atlas. The SUV_max and mean 50% isocontour SUV (SUV_iso) of primary, locally recurrent, and metastatic lesions were compared between the 2 reconstruction methods using linear mixed-effects models. In addition, mean SUVs were obtained from bone marrow in the third lumbar vertebra (L3) to investigate the effect of including bone attenuation on lesion-to-bone marrow SUV ratios (SUVR_max and SUVR_iso; recurrence study only). The 5-compartment attenuation maps were visually compared with the in-phase Dixon MR images for evaluation of bone registration errors near the lesions. P values of less than 0.05 were considered significant. Results: Sixty-two lesions from 39 patients were evaluated. Bone registration errors were found near 19 (31%) of these lesions. In the remaining 8 primary prostate tumors, 7 locally recurrent lesions, and 28 lymph node metastases without bone registration errors, use of the 5-compartment attenuation map was associated with small but significant increases in SUV_max (2.5%; 95% confidence interval [CI], 2.0%-3.0%; P < 0.001) and SUV_iso (2.5%; 95% CI, 1.9%-3.0%; P < 0.001), but not SUVR_max (0.2%; 95% CI, -0.5%-0.9%; P = 0.604) and SUVR_iso (0.2%; 95% CI -0.6%-1.0%; P = 0.581), in comparison to the 4-compartment attenuation map. Conclusion: The investigated method for atlas-based inclusion of bone in ¹⁸F-fluciclovine PET/MRI attenuation correction has only a small effect on the SUVs of soft-tissue prostate cancer lesions, and no effect on their lesion-to-bone marrow SUVRs when using signal from L3 as a reference. The attenuation maps should always be checked for registration artifacts for lesions in or close to the bones.

Update on 18F-Fluciclovine PET for Prostate Cancer Imaging

PET is a functional imaging method that can exploit various aspects of tumor biology to enable greater detection of prostate cancer than can be provided by morphologic imaging alone. Anti-1-amino-3-18F-flurocyclobutane-1-carboxylic acid (18F-fluciclovine) is a nonnaturally occurring amino acid PET radiotracer that was recently approved by the U.S. Food and Drug Administration for detection of suspected recurrent prostate cancer. The tumor-imaging features of this radiotracer mirror the upregulation of transmembrane amino acid transport that occurs in prostate cancer because of increased amino acid metabolism for energy and protein synthesis. This continuing medical education article provides an overview on 18F-fluciclovine PET diagnostic capabilities for primary and metastatic disease, including reviews of published comparisons to conventional imaging and other molecular imaging agents. Additionally, the imaging procedure and image interpretation are detailed, including physiologic and pathologic uptake patterns and pitfalls.