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

The role of brown adipose tissue in branched-chain amino acid clearance in people

Brown adipose tissue (BAT) in rodents appears to be an important tissue for the clearance of plasma branched-chain amino acids (BCAAs) contributing to improved metabolic health. However, the role of human BAT in plasma BCAA clearance is poorly understood. Here, we evaluate patients with prostate cancer who underwent positron emission tomography-computed tomography imaging after an injection of 18F-fluciclovine (L-leucine analog). Supraclavicular adipose tissue (AT; primary location of human BAT) has a higher net uptake rate for 18F-fluciclovine compared to subcutaneous abdominal and upper chest AT. Supraclavicular AT 18F-fluciclovine net uptake rate is lower in patients with obesity and type 2 diabetes. Finally, the expression of genes involved in BCAA catabolism is higher in the supraclavicular AT of healthy people with high BAT volume compared to those with low BAT volume. These findings support the notion that BAT can potentially function as a metabolic sink for plasma BCAA clearance in people.

Personalizing approaches to the management of metastatic hormone sensitive prostate cancer: role of advanced imaging, genetics and therapeutics

PURPOSE

To summarize contemporary and emerging strategies for the diagnosis and management of metastatic hormone sensitive prostate cancer (mHSPC), focusing on diagnostic testing and therapeutics.

METHODS

Literature review using PUBMED-Medline databases as well as clinicaltrials.gov to include reported or ongoing clinical trials on treatment for mHSPC. We prioritized the findings from phase III randomized clinical trials, systematic reviews, meta-analyses and clinical practice guidelines.

RESULTS

There have been significant changes to the diagnosis and staging evaluation of mHSPC with the integration of increasingly accurate positron emission tomography (PET) imaging tracers that exceed the performance of conventional computerized tomography (CT) and bone scan. Germline multigene testing is recommended for the evaluation of patients newly diagnosed with mHSPC given the prevalence of actionable alterations that may create candidacy for specific therapies. Although androgen deprivation therapy (ADT) remains the backbone of treatment for mHSPC, approaches to first-line treatment include the integration of multiple agents including androgen receptor synthesis inhibitors (ARSI; abiraterone) Androgen Receptor antagonists (enzalutamide, darolutamide, apalautamide), and docetaxel chemotherapy. The combination of ADT, ARSI, and docetaxel chemotherapy has recently been evaluated in a randomized trial and was associated with significantly improved overall survival including in patients with a high burden of disease. The role of local treatment to the prostate with radiation has been evaluated in randomized trials with additional studies underway evaluating the role of cytoreductive radical prostatectomy.

CONCLUSION

The staging and initial management of patients with mHSPC has undergone significant advances in the last decade with advancements in the diagnosis, treatment and sequencing of therapies.

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.

18F-Fluciclovine versus PSMA PET Imaging in Primary Tumor Detection during Initial Staging of High-Risk Prostate Cancer: A Systematic Review and Meta-Analysis

Purpose Fluorine 18 (18F)-fluciclovine and prostate-specific membrane antigen (PSMA) tracers are commonly used for localizing biochemical recurrence of prostate cancer, but their accuracy in primary tumor detection in the initial staging of high-risk prostate cancer has not been established. Materials and Methods A systematic review was performed of the electronic databases for original studies published between 2012 and 2020. Included studies were those in which 18F-fluciclovine or PSMA PET was used for initial staging of patients with high-risk prostate cancer. The diagnostic performance data were collected for primary tumor with histopathologic results as reference standard. The Quality Assessment of Diagnostic Accuracy Studies-2 tool was used for quality appraisal. A random-effects model was used to summarize the effect sizes and to evaluate the difference between two groups. Results Overall, 28 studies met the eligibility criteria, and 17 were included in the meta-analysis (18F-fluciclovine = 4, PSMA = 13). Of these 17 studies, 12 (70%) were judged to have high risk of bias in one of the evaluated domains, and nine studies were deemed to have applicability concerns. The pooled sensitivity, specificity, and diagnostic odds ratio for 18F-fluciclovine versus PSMA were 85% (95% CI: 73%, 92%) versus 84% (95% CI: 77%, 89%) (P = .78), 77% (95% CI: 60%, 88%) versus 83% (95% CI: 76%, 89%) (P = .40), and 18.88 (95% CI: 5.01, 71.20) versus 29.37 (95% CI: 13.35, 64.60) (P = .57), respectively, with no significant difference in diagnostic test accuracy. Conclusion 18F-fluciclovine and PSMA PET demonstrated no statistically significant difference in diagnostic accuracy in primary tumor detection during initial staging of high-risk prostate cancer. Keywords: PET, Prostate, Molecular Imaging-Cancer, Staging Supplemental material is available for this article. © RSNA, 2022.

New imaging modalities to consider for men with prostate cancer on active surveillance

PURPOSE

To discuss the potential utility of newer imaging modalities including micro-ultrasound and PSMA-PET for the detection of clinically significant prostate cancer, technologies that may gain roles as adjuncts to multiparametric magnetic resonance imaging (mpMRI) in the active surveillance (AS) setting.

METHODS

Narrative review of two new imaging modalities used for primary prostate cancer through April 2021. A targeted search was performed to identify current relevant literature on the role of new imaging modalities for primary prostate cancer using search terms "micro-ultrasound," "molecular imaging," "prostate cancer," "active surveillance," "multiparametric MRI," "PI-RADS," "PRI-MUS," and "detection rate." In addition, references of included articles were screened for further relevant publications.

RESULTS

Micro-ultrasound (micro-US) and prostate-specific membrane antigen-positron emission tomography (PSMA-PET) are increasing in their use and applicability to prostate cancer imaging. Micro-US is used for cancer detection and may identify higher grade cancers more accurately than conventional ultrasound, despite technical hurdles in its initial launch. PSMA-PET is highly sensitive and specific for high-grade and metastatic prostate cancer, though costly and not easily available. Though data are sparse, it may have an emerging role in cancer diagnosis in select localized cases, and in some men considering (or currently on) AS who have indications of more aggressive disease.

CONCLUSION

There are very limited data on micro-US and PSMA-PET in AS patients. However, given the ability of these modalities to identify high-grade cancer, their judicious use in AS patients may be of utility in the future.

PSA and PSA Kinetics as Predictors for 18F-Fluciclovine PET/CT Positivity in Biochemically Recurrent Prostate Cancer

INTRODUCTION

18F-Fluciclovine PET/CT is one of the imaging techniques currently employed to restage prostate cancer (PCa). Due to the conflicting results reported in the literature, it is not yet known at what PSA threshold 18F-fluciclovine PET/CT could reliably demonstrate the presence of recurring disease. We explored the association between 18F-fluciclovine PET/CT positivity and prescan PSA, PSA doubling time, and PSA velocity in patients with biochemical recurrence (BCR) of PCa after curative-intent treatment.

METHODS

Data from 59 patients who underwent 18F-fluciclovine PET/CT for BCR after radical prostatectomy or radiotherapy were retrieved from a single institution database. Patients already undergone salvage treatments at the time of PET/CT, with newly diagnosed PCa or with initial diagnosis of metastatic PCa were excluded. A 2-sided independent samples Bayesian t test and Bayesian Mann-Whitney U test were used to assess the association between PET/CT and prescan PSA, PSA doubling time, and PSA velocity.

RESULTS

Evidence for no difference between PET/CT-positive and -negative patients for log-transformed PSA was found (BF01 3.61, % error: 0.01). Robustness check and sequential analysis showed stability across a wide range of prior distribution specifications. The hypothesis of no difference in terms of PSA-dt and for PSA-vel between groups was found to be more likely compared to the alternative hypothesis (BF01 of 3.44 and 3.48, respectively).

CONCLUSION

PSA and PSA kinetics are unlikely to be associated with 18F-fluciclovine PET/CT positivity in patients with BCR, and none of these serum biomarkers might be used as single predictors of PET/CT detection. Larger studies might be needed to evaluate the role of different predictors.

[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.

The Role of [18F]Fluciclovine PET/CT in the Characterization of High-Risk Primary Prostate Cancer: Comparison with [11C]Choline PET/CT and Histopathological Analysis

Simple Summary

The role of [¹⁸F]Fluciclovine Positron Emission Tomography/Computed Tomography (PET/CT) in the characterization of intra-prostatic lesions was evaluated in high-risk primary PCa patients, scheduled for radical surgery, comparing investigational [¹⁸F]Fluciclovine and conventional [¹¹C]Choline PET/CT results with the reference standard of pathologic surgical specimen. PET visual and semi-quantitative analyses were performed: for instance, patient-based, blinded to histopathology; subsequently lesion-based, unblinded, according to a pathology reference mapping. Among 19 pts, 45 malignant and 31 benign lesions were found. The highest SUVmax matched with the lobe of the index lesion in 89% of pts and a direct correlation between [¹⁸F]Fluciclovine uptake values and pISUP was demonstrated. Overall, the lesion-based performance of PET semiquantitative parameters (SUVmax, Target to background Ratio-TBRs) with either [¹⁸F]Fluciclovine or [¹¹C]Choline, in detecting either malignant/ISUP2-5/ISUP4-5 PCa lesions, was moderate and similar (AUCs ≥ 0.70), but still inadequate (AUCs ≤ 0.81) as standalone staging procedure. TBRs (especially with threshold higher than bone marrow) may be complementary to implement malignancy targeting.

Abstract

The primary aim of the study was to evaluate the role of [¹⁸F]Fluciclovine PET/CT in the characterization of intra-prostatic lesions in high-risk primary PCa patients eligible for radical prostatectomy, in comparison with conventional [¹¹C]Choline PET/CT and validated by prostatectomy pathologic examination. Secondary aims were to determine the performance of PET semi-quantitative parameters (SUVmax; target-to-background ratios [TBRs], using abdominal aorta, bone marrow and liver as backgrounds) for malignant lesion detection (and best cut-off values) and to search predictive factors of malignancy. A six sextants prostate template was created and used by PET readers and pathologists for data comparison and validation. PET visual and semi-quantitative analyses were performed: for instance, patient-based, blinded to histopathology; subsequently lesion-based, un-blinded, according to the pathology reference template. Among 19 patients included (mean age 63 years, 89% high and 11% very-high-risk, mean PSA 9.15 ng/mL), 45 malignant and 31 benign lesions were found and 19 healthy areas were selected (n = 95). For both tracers, the location of the “blinded” prostate SUVmax matched with the lobe of the lesion with the highest pGS in 17/19 cases (89%). There was direct correlation between [¹⁸F]Fluciclovine uptake values and pISUP. Overall, lesion-based (n = 95), the performance of PET semiquantitative parameters, with either [¹⁸F]Fluciclovine or [¹¹C]Choline, in detecting either malignant/ISUP2-5/ISUP4-5 PCa lesions, was moderate and similar (AUCs ≥ 0.70) but still inadequate (AUCs ≤ 0.81) as a standalone staging procedure. A [¹⁸F]Fluciclovine TBR-L3 ≥ 1.5 would depict a clinical significant lesion with a sensitivity and specificity of 85% and 68% respectively; whereas a SUVmax cut-off value of 4 would be able to identify a ISUP 4-5 lesion in all cases (sensitivity 100%), although with low specificity (52%). TBRs (especially with threshold significantly higher than aorta and slightly higher than bone marrow), may be complementary to implement malignancy targeting.

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.

Patterns of Lymph Node Failure in Patients With Recurrent Prostate Cancer Postradical Prostatectomy and Implications for Salvage Therapies

PURPOSE

There is increasing use of radical prostatectomy to treat patients with high-risk prostate cancer. This has contributed toward a pathologic stage migration, and a greater number of patients are subsequently being diagnosed with biochemical failure. There is increasing use of advanced imaging techniques in the setting of biochemical failure, including positron emission tomography-computed tomography (PET-CT).

METHODS AND MATERIALS

This critical literature review highlights the evidence for PET-CT in postprostatectomy biochemical failure and identifies sites of pelvic lymph node relapse in the setting of biochemical failure and the potential implications that the locations of these relapses may have for salvage therapies. Potential future directions are then considered.

RESULTS

The optimal PET-CT tracer remains uncertain but there is increasing use of prostate-specific membrane antigen PET-CT for investigating sites of nodal metastasis at low prostate-specific antigen levels, and this is leading to a blurring of the biochemical and radiologic recurrence phases. The optimal therapeutic approach remains undefined, with current trials investigating postoperative radiation therapy to the whole pelvis in addition to the prostatic fossa, the use of PET-CT in the setting of biochemical recurrence to guide delivery of salvage radiation therapy, and, for patients with node-only relapsed prostate cancer, the addition of whole pelvis radiation therapy to metastasis-directed therapies such as stereotactic ablative radiotherapy.

CONCLUSIONS

The most appropriate target volume for salvage radiation therapy remains uncertain, and the findings of studies using PET-CT to map nodal recurrences suggest that there could be a role for extending whole pelvis radiation therapy volumes to increase coverage of superior nodal regions. The emerging fields of radiomics and radiogenomics could provide important prognostic information and aid decision making for patients with relapsed prostate cancer.

Diagnostic Performance of PET Imaging Using Different Radiopharmaceuticals in Prostate Cancer According to Published Meta-Analyses

A significant number of meta-analyses reporting data on the diagnostic performance of positron emission tomography (PET) in prostate cancer (PCa) is currently available in the literature. In particular, different PET radiopharmaceuticals were used for this purpose. The aim of this review is to summarize information retrieved by published meta-analyses on this topic. The first step included a systematic search of the literature (last search date: June 2020), screening two databases (PubMed/MEDLINE and Cochrane Library). This combination of key words was used: (A) “PET” OR “positron emission tomography” AND (B) “prostate” OR “prostatic” AND (C) meta-analysis. Only meta-analyses on Positron Emission Tomography/Computed Tomography (PET/CT) or Positron Emission Tomography/Magnetic Resonance (PET/MR) in PCa were selected. We have summarized the diagnostic performance of PET imaging in PCa, taking into account 39 meta-analyses published in the literature. Evidence-based data showed the good diagnostic performance of PET/CT with several radiopharmaceuticals, including prostate-specific membrane antigen (PSMA)-targeted agents, radiolabeled choline, fluciclovine, and fluoride in restaging and staging settings. Less evidence-based data were available for PET/MR with different radiotracers. More prospective multicentric studies and cost-effectiveness analyses are warranted.

The Role of PET-CT Imaging in Prostate Cancer

Prostate cancer is the commonest malignancy to affect men in the United Kingdom. Extraprostatic disease detection at staging and in the setting of biochemical recurrence is essential in determining treatment strategy. Conventional imaging including computed tomography and bone scintigraphy are limited in their ability to detect sites of loco-regional nodal and metastatic bone disease, particularly at clinically relevant low prostate-specific antigen levels. The use of positron emission tomography-computed tomography has helped overcome these deficiencies and is leading a paradigm shift in the management of prostate cancer using a wide range of radiopharmaceuticals. Their mechanisms of action, utility in both staging and biochemical recurrence, and comparative strengths and weaknesses will be covered in this article.

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.