Positron emission tomography (PET) in primary prostate cancer staging and risk assessment

Automated radiosynthesis and preclinical evaluation of two new PSMA-617 derivatives radiolabelled via [18F]AlF2+ method

BACKGROUND

In the last decade the development of new PSMA-ligand based radiopharmaceuticals for the imaging and therapy of prostate cancer has been a highly active and important area of research. The most promising derivative in terms of interaction with the antigen and clinical properties has been found to be "PSMA-617", and its lutetium-177 radiolabelled version has recently been approved by EU and USA regulatory agencies for therapeutic purposes. For the above reasons, the development of new derivatives of PSMA-617 radiolabelled with fluorine-18 may still be of great interest. This paper proposes the comparison of two different PSMA-617 derivatives functionalized with NODA and RESCA chelators, respectively, radiolabelled via [18F]AlF2+ complexation.

RESULTS

The organic synthesis of two PSMA-617 derivatives and their radiolabelling via [18F]AlF2+ complexation resulted to proceed efficiently and successfully. Moreover, stability in solution and in plasma has been evaluated. The whole radiosynthesis procedure has been fully automated, and the final products have been obtained with radiochemical yield and purity potentially suitable for clinical studies. The biodistribution of the two derivatives was performed both in prostate cancer and glioma tumour models. Compared with the reference [18F]F-PSMA-1007 and [18F]F-PSMA-617-RESCA, [18F]F-PSMA-617-NODA derivative showed a higher uptake in both tumors, faster clearance in non-target organs, and lower uptake in salivary glands.

CONCLUSION

PSMA-617 NODA and RESCA derivatives were radiolabelled successfully via [18F]AlF2+ chelation, the former being more stable in solution and human plasma. Moreover, preclinical biodistribution studies showed that [18F]F-PSMA-617-NODA might be of potential interest for clinical applications.

Radiotheranostics in advanced prostate cancer: Current and future directions

The discovery of small molecules that target the extracellular domain of prostate-specific membrane antigen (PSMA) has led to advancements in diagnostic imaging and the development of precision radiopharmaceutical therapies. In this review, we present the available existing data and highlight the key ongoing clinical evaluations of PSMA-based imaging in the management of primary, biochemically recurrent, and metastatic prostate cancer. We also discuss clinical studies that explore the use of PSMA-based radiopharmaceutical therapy (RPT) in metastatic prostate cancer and forthcoming trials that investigate PSMA RPT in earlier disease states. Multidisciplinary collaboration in clinical trial design and therapeutic administration is critical to the continued progress of this evolving radiotheranostics field.

Cost-Effectiveness Modeling of Prostate-Specific Membrane Antigen Positron Emission Tomography with Piflufolastat F 18 for the Initial Diagnosis of Patients with Prostate Cancer in the United States

BACKGROUND AND OBJECTIVES

Piflufolastat F 18 is a novel prostate-specific membrane antigen (PSMA)-targeted positron emission tomography (PET) radiotracer that is superior to standard of care (SOC) imaging for the initial staging of prostate cancer and the detection of biochemical recurrence. As piflufolastat F 18 has been approved in the United States (US) for this indication, this modeling study assessed the cost effectiveness of piflufolastat F 18 versus fluciclovine F-18, gallium68-PSMA-11 (PSMA 11), and SOC imaging (a mix of bone scans, computed tomography, and magnetic resonance imaging) for the diagnosis and staging of prostate cancer from a US healthcare system perspective.

PERSPECTIVE

A US third-party payer perspective was used, which for this population reflects a mix of commercial and Medicare, considering only direct healthcare costs.

SETTING

This study utilized a tertiary healthcare setting.

METHODS

A decision tree was used to map the diagnostic/treatment pathway, consisting of the proportion of patients with local, regional, distant, or no disease; prostate-specific antigen (PSA) ≤ 1.0 or > 1.0; and accuracy of imaging modalities. A Markov model predicted the long-term outcomes of disease progression according to treatment decisions. Inputs to the model were informed by data from the OSPREY and CONDOR clinical trials, public data, and the literature. Treatment mix included active surveillance, radiation therapy, prostatectomy, androgen deprivation therapy (ADT), and radiation therapy + ADT, informed by expert opinion. Outcomes included life-years (LY), quality-adjusted life-years (QALY), and the incremental cost-effectiveness ratio (ICER). All costs were reported in 2021 US dollars, using the US Bureau of Labor Statistics Consumer Price Index. A willingness-to-pay (WTP) threshold of $150,000 was considered cost effective, consistent with the upper range used as the standard for price benchmarks by the Institute for Clinical and Economic Review. The robustness of the base-case results was assessed in deterministic and probabilistic sensitivity analyses.

RESULTS

Over a lifetime horizon, piflufolastat F 18 had the greatest effectiveness in terms of LYs (6.80) and QALYs (5.33); for the comparators, LYs ranged from 6.58 (SOC) to 6.76 (PSMA 11) and QALYs ranged from 5.12 (SOC) and 5.30 (PSMA 11). Piflufolastat F 18 was more cost effective compared with fluciclovine F 18, PSMA 11, and SOC, with ICERs of $21,122, $55,836, and $124,330 per QALY gained, respectively. Piflufolastat F 18 was associated with the greatest net monetary benefit ($627,918) compared with the other options at a WTP threshold of $150,000. The results of the deterministic and probabilistic sensitivity analyses supported the robustness of the base-case results.

CONCLUSIONS

This study suggests that piflufolastat F 18 is a cost-effective diagnostic option for men with prostate cancer in the US, with higher associated LY, QALY, and greater net monetary benefit than fluciclovine F 18, PSMA 11, and SOC imaging.

Periprostatic Adipose Tissue: A New Perspective for Diagnosing and Treating Prostate Cancer

Prostate cancer (PCa) is the most common tumor of the male genitourinary system. It will eventually progress to fatal metastatic castration-resistant prostate cancer, for which treatment options are limited. Adipose tissues are distributed in various parts of the body. They have different morphological structures and functional characteristics and are associated with the development of various tumors. Periprostatic adipose tissue (PPAT) is the closest white visceral adipose tissue to the prostate and is part of the PCa tumor microenvironment. Studies have shown that PPAT is involved in PCa development, progression, invasion, and metastasis through the secretion of multiple active molecules. Factors such as obesity, diet, exercise, and organochlorine pesticides can affect the development of PCa indirectly or directly through PPAT. Based on the mechanism of PPAT's involvement in regulating PCa, this review summarized various diagnostic and therapeutic approaches for PCa with potential applications to assess the progression of patients' disease and improve clinical outcomes.

Detecting and Locating the Site of Local Relapse Using 18F-PSMA-1007 Imaging After Primary Treatment of 135 Prostate Cancer Patients-Potential Impact on PSMA-Guided Radiation Therapy

PURPOSE

Due to limited imaging options, the visualization of a local relapse of prostate cancer used to pose a considerable challenge. However, since the integration of ¹⁸F-PSMA-1007-PET/CT into the clinic, a relapsed tumor can now easily be detected by hybrid imaging. The present study aimed to evaluate and map the allocate relapse in a large cohort of prostate cancer patients focusing on individual patient management conclusions for radiation therapy.

PROCEDURES

The current study included 135 men with prostate cancer after primary treatment who underwent ¹⁸F-PSMA-1007-PET/CT due to biochemical relapse detecting a local relapse. Imaging data were reassessed and analyzed with regard to relapse locations. For the correlation of tumor foci with clinical data, we used binary logistic regression models as well as the Kruskal-Wallis test and Mann-Whitney test.

RESULTS

In total, 69.6% of all patients (mean age: 65 years) underwent prostatectomy while 30.4% underwent radiation therapy. PET imaging detected most frequently a unifocal relapse (72.6%). There was a statistically significantly higher rate of ipsilateral cases among the relapsed tumors. Comparing both treatment approaches, tumors relapsed most commonly within the posterior region after surgery and transition/peripheral zone after radiation therapy, respectively.

CONCLUSIONS

The present study confirms that ¹⁸F-PSMA-1007-PET/CT is highly suitable for the localization and allocation of a local relapse in patients with prostate cancer. The data enable further optimizing dose prescriptions and target volume delineations of radiation therapy in the future.

Alteration of Lipid Metabolism in Prostate Cancer: Multifaceted Oncologic Implications

Cancer is increasingly recognized as an extraordinarily heterogeneous disease featuring an intricate mutational landscape and vast intra- and intertumor variability on both genetic and phenotypic levels. Prostate cancer (PCa) is the second most prevalent malignant disease among men worldwide. A single metabolic program cannot epitomize the perplexing reprogramming of tumor metabolism needed to sustain the stemness of neoplastic cells and their prominent energy-consuming functional properties, such as intensive proliferation, uncontrolled growth, migration, and invasion. In cancerous tissue, lipids provide the structural integrity of biological membranes, supply energy, influence the regulation of redox homeostasis, contribute to plasticity, angiogenesis and microenvironment reshaping, mediate the modulation of the inflammatory response, and operate as signaling messengers, i.e., lipid mediators affecting myriad processes relevant for the development of the neoplasia. Comprehensive elucidation of the lipid metabolism alterations in PCa, the underlying regulatory mechanisms, and their implications in tumorigenesis and the progression of the disease are gaining growing research interest in the contemporary urologic oncology. Delineation of the unique metabolic signature of the PCa featuring major aberrant pathways including de novo lipogenesis, lipid uptake, storage and compositional reprogramming may provide novel, exciting, and promising avenues for improving diagnosis, risk stratification, and clinical management of such a complex and heterogeneous pathology.

The Detection Performance of 18 F-Prostate-Specific Membrane Antigen-1007 PET/CT in Primary Prostate Cancer : A Systemic Review and Meta-analysis

BACKGROUND

Multiple tools are now available to determine the requirement for a biopsy to diagnose prostate cancer, and PET/CT with radiolabeled prostate-specific membrane antigen (PSMA)-targeting radiotracers has been recommended for detecting primary prostate cancer. Particularly, the radiotracer 18 F-PSMA-1007 was found to be more favorable for primary tumors compared with other PSMA-targeting radiotracers because of its low clearance via the urinary tract and better image resolution. Thus, we performed a systematic review and meta-analysis to more accurately evaluate the detection performance of 18 F-PSMA-1007 PET/CT in primary prostate cancer patients.

METHODS

An update on the databases of PubMed/MEDLINE, EMBASE, and Cochrane Library for comprehensive literature search was performed on September 30, 2021. The pooling detection rate was calculated on a per-patient basis. The pooling median of the SUV max was analyzed from the included studies. Furthermore, the positive predictive value of 18 F-PSMA-1007 PET/CT with pathologic lesions was analyzed using the criterion standard.

RESULTS

Twelve studies (540 patients total) were included in the meta-analysis. The overall pooling detection rate of 18 F-PSMA-1007 per patient was 94%, and the pooling median of SUV max located at the intraprostate tumor was 16 (range, 3.7-77.7). The positive predictive value of 18 F-PSMA-1007 per lesion with histopathological validation was 0.90, detecting regional lymph node metastasis was 0.94, and detecting localized prostatic tumors was 0.84.

CONCLUSIONS

In the current meta-analysis, we revealed the excellent performance of 18 F-PSMA-1007 to detect localized prostatic tumor lesions and regional lymph node metastasis. Moreover, the uptake of localized tumors in primary prostate cancer was nearly liver uptake and may be considered a suspicious malignancy if it was equal to or greater than the liver uptake.

Multiple metabolic pathways fuel the truncated tricarboxylic acid cycle of the prostate to sustain constant citrate production and secretion

Objective

The prostate is metabolically unique: it produces high levels of citrate for secretion via a truncated tricarboxylic acid (TCA) cycle to maintain male fertility. In prostate cancer (PCa), this phenotype is reprogrammed, making it an interesting therapeutic target. However, how the truncated prostate TCA cycle works is still not completely understood.

Methods

We optimized targeted metabolomics in mouse and human organoid models in ex vivo primary culture. We then used stable isotope tracer analyses to identify the pathways that fuel citrate synthesis.

Results

First, mouse and human organoids were shown to recapitulate the unique citrate-secretory program of the prostate, thus representing a novel model that reproduces this unusual metabolic profile. Using stable isotope tracer analysis, several key nutrients were shown to allow the completion of the prostate TCA cycle, revealing a much more complex metabolic profile than originally anticipated. Indeed, along with the known pathway of aspartate replenishing oxaloacetate, glutamine was shown to fuel citrate synthesis through both glutaminolysis and reductive carboxylation in a GLS1-dependent manner. In human organoids, aspartate entered the TCA cycle at the malate entry point, upstream of oxaloacetate. Our results demonstrate that the citrate-secretory phenotype of prostate organoids is supported by the known aspartate–oxaloacetate–citrate pathway, but also by at least three additional pathways: glutaminolysis, reductive carboxylation, and aspartate–malate conversion.

Conclusions

Our results add a significant new dimension to the prostate citrate-secretory phenotype, with at least four distinct pathways being involved in citrate synthesis. Better understanding this distinctive citrate metabolic program will have applications in both male fertility as well as in the development of novel targeted anti-metabolic therapies for PCa.

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Targeted metabolomics and stable isotope tracer analysis were optimized in mouse and human prostate organoids.

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Organoids recapitulate the unique citrate-secretory phenotype of the prostate.

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Glutamine fuels citrate synthesis for secretion by glutaminolysis and reductive carboxylation.

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Aspartate enters the TCA cycle at different entry points in mouse and human prostate organoids for citrate production.

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We revealed a much more complex TCA cycle in the prostate than originally anticipated.

Prostate-specific membrane antigen (PSMA) fusion imaging in prostate cancer: PET-CT vs PET-MRI

OBJECTIVES

To investigate whether PET-CT or PET-MRI is more appropriate for imaging prostate cancer, in terms of primary tumor detection, local staging and recurrence, as well as lymph nodes and distant metastases.

METHODS

A systematic literature search was conducted on Embase, PubMed/MEDLINE, and the Cochrane Library database. Studies evaluating the diagnostic performance of PET-CT vs PET-MRI in prostate cancer patients were emphasized.

RESULTS

We reviewed 57 original research articles during the period 2016-2021: 14 articles regarding the radiotracer PSMA; 18 articles regarding the primary tumor detection, local tumor staging, managing local recurrence; 17 articles for managing lymph node metastases; and eight articles for managing bone and other distant metastases. PSMA PET could be complementary to mpMRI for primary prostate cancer localization and is particularly valuable for PI-RADS three lesions. PET-MRI is better than PET-CT in local tumor staging due to its specific benefit in predicting extracapsular extension in MRI-occult prostate cancer patients. PET-MRI is likely superior as compared with PET-CT in detecting local recurrence, and has slightly higher detection rates than PET-CT in lymph node recurrence. PET-CT and PET-MRI seem to have equivalent performance in detecting distant bony or visceral metastases.

CONCLUSION

In conclusion, PET-MRI is suitable for local and regional disease, either primary staging or restaging, whereas PET-CT is valuable for managing distant bony or visceral metastasis.

ADVANCES IN KNOWLEDGE

We reviewed the emerging applications of PET-MRI and PET-CT in clinical aspects. Readers will gain an objective overview on the strength and shortfalls of PET-MRI or PET-CT in the management of prostate cancer.

Bone Marrow Activation After Chemotherapy Presenting as Diffuse Skeletal Uptake on 18F-Fluorocholine PET/CT

ABSTRACT

Diffuse 18F-FDG skeletal uptake due to chemotherapy-induced bone marrow activation is well documented, whereas it has never been reported with 18F-fluorocholine. We described a patient with pelvic recurrence of prostate cancer at 18F-fluorocholine PET/CT. A second PET/CT after docetaxel showed minimal residual activity in pelvis, but it revealed diffuse, intense 18F-fluorocholine skeletal uptake. Considering biochemical and metabolic response and absence of morphologically suspected bone lesions, skeletal hyperactivity was interpreted as chemotherapy-related bone marrow rebound rather than diffuse metastatic involvement, as confirmed by its resolution after treatment ended. The occurrence of such 18F-fluorocholine pattern should be considered to avoid imaging misinterpretation.

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.

New Frontiers in Molecular Imaging Using Peptide-Based Radiopharmaceuticals for Prostate Cancer

The high incidence of prostate cancer (PCa) increases the need for progress in its diagnosis, staging, and precise treatment. The overexpression of tumor-specific receptors for peptides in human cancer cells, such as gastrin-releasing peptide receptor, natriuretic peptide receptor, and somatostatin receptor, has indicated the ideal molecular basis for targeted imaging and therapy. Targeting these receptors using radiolabeled peptides and analogs have been an essential topic on the current forefront of PCa studies. Radiolabeled peptides have been used to target receptors for molecular imaging in human PCa with high affinity and specificity. The radiolabeled peptides enable optimal quick elimination from blood and normal tissues, producing high contrast for positron emission computed tomography and single-photon emission computed tomography imaging with high tumor-to-normal tissue uptake ratios. Owing to their successful application in visualization, peptide derivatives with therapeutic radionuclides for peptide receptor radionuclide therapy in PCa have been explored in recent years. These developments offer the promise of personalized, molecular medicine for individual patients. Hence, we review the preclinical and clinical literature in the past 20 years and focus on the newer developments of peptide-based radiopharmaceuticals for the imaging and therapy of PCa.

Prognostic Value of CT-Attenuation and 18F-Fluorodeoxyglucose Uptake of Periprostatic Adipose Tissue in Patients with Prostate Cancer

This study aimed to assess the prognostic value of computed tomography (CT)-attenuation and ¹⁸F-fluorodeoxyglucose (FDG) uptake of periprostatic adipose tissue (PPAT) for predicting disease progression-free survival (DPFS) in patients with prostate cancer. Seventy-seven patients with prostate cancer who underwent staging FDG positron emission tomography (PET)/CT were retrospectively reviewed. CT-attenuation (HU) and FDG uptake (SUV) of PPAT were measured from the PET/CT images. The relationships between these PPAT parameters and clinical factors were assessed, and a Cox proportional hazard regression test was performed to evaluate the prognostic significance of PPAT HU and SUV. PPAT HU and SUV showed significant positive correlations with tumor stage and serum prostate-specific antigen level (PSA) (p < 0.05). Patients with high PPAT HU and SUV had significantly worse DPFS than those with low PPAT HU and SUV (p < 0.05). In multivariate analysis, PPAT SUV was a significant predictor of DPFS after adjusting for tumor stage, serum PSA, and tumor SUV (p = 0.003; hazard ratio, 1.50; 95% confidence interval, 1.15–1.96). CT-attenuation and FDG uptake of PPAT showed significant association with disease progression in patients with prostate cancer. These imaging findings may be evidence of the role of PPAT in prostate cancer progression.

Modular Medical Imaging Agents Based on Azide-Alkyne Huisgen Cycloadditions: Synthesis and Pre-Clinical Evaluation of 18 F-Labeled PSMA-Tracers for Prostate Cancer Imaging

Since the seminal contribution of Rolf Huisgen to develop the [3+2] cycloaddition of 1,3-dipolar compounds, its azide-alkyne variant has established itself as the key step in numerous organic syntheses and bioorthogonal processes in materials science and chemical biology. In the present study, the copper(I)-catalyzed azide-alkyne cycloaddition was applied for the development of a modular molecular platform for medical imaging of the prostate-specific membrane antigen (PSMA), using positron emission tomography. This process is shown from molecular design, through synthesis automation and in vitro studies, all the way to pre-clinical in vivo evaluation of fluorine-18- labeled PSMA-targeting 'F-PSMA-MIC' radiotracers (t1/2 =109.7 min). Pre-clinical data indicate that the modular PSMA-scaffold has similar binding affinity and imaging properties to the clinically used [68 Ga]PSMA-11. Furthermore, we demonstrated that targeting the arene-binding in PSMA, facilitated through the [3+2]cycloaddition, can improve binding affinity, which was rationalized by molecular modeling. The here presented PSMA-binding scaffold potentially facilitates easy coupling to other medical imaging moieties, enabling future developments of new modular imaging agents.

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.

Tumour metabolism and its unique properties in prostate adenocarcinoma

Anabolic metabolism mediated by aberrant growth factor signalling fuels tumour growth and progression. The first biochemical descriptions of the altered metabolic nature of solid tumours were reported by Otto Warburg almost a century ago. Now, the study of tumour metabolism is being redefined by the development of new molecular tools, tumour modelling systems and precise instrumentation together with important advances in genetics, cell biology and spectroscopy. In contrast to Warburg's original hypothesis, accumulating evidence demonstrates a critical role for mitochondrial metabolism and substantial variation in the way in which different tumours metabolize nutrients to generate biomass. Furthermore, computational and experimental approaches suggest a dominant influence of the tissue-of-origin in shaping the metabolic reprogramming that enables tumour growth. For example, the unique metabolic properties of prostate adenocarcinoma are likely to stem from the distinct metabolism of the prostatic epithelium from which it emerges. Normal prostatic epithelium employs comparatively glycolytic metabolism to sustain physiological citrate secretion, whereas prostate adenocarcinoma consumes citrate to power oxidative phosphorylation and fuel lipogenesis, enabling tumour progression through metabolic reprogramming. Current data suggest that the distinct metabolic aberrations in prostate adenocarcinoma are driven by the androgen receptor, providing opportunities for functional metabolic imaging and novel therapeutic interventions that will be complementary to existing diagnostic and treatment options.

Advanced PET imaging in oncology: status and developments with current and future relevance to lung cancer care

PURPOSE OF REVIEW

This review highlights the status and developments of PET imaging in oncology, with particular emphasis on lung cancer. We discuss the significance of PET for diagnosis, staging, decision-making, monitoring of treatment response, and drug development. The PET key advantage, the noninvasive assessment of functional and molecular tumor characteristics including tumor heterogeneity, as well as PET trends relevant to cancer care are exemplified.

RECENT FINDINGS

Advances of PET and radiotracer technology are encouraging for multiple fields of oncological research and clinical application, including in-depth assessment of PET images by texture analysis (radiomics). Whole body PET imaging and novel PET tracers allow assessing characteristics of most types of cancer. However, only few PET tracers in addition to F-fluorodeoxyglucose have sufficiently been validated, approved, and are reimbursed for a limited number of indications. Therefore, validation and standardization of PET parameters including tracer dosage, image acquisition, post processing, and reading are required to expand PET imaging as clinically applicable approach.

SUMMARY

Considering the potential of PET imaging for precision medicine and drug development in lung and other types of cancer, increasing efforts are warranted to standardize PET technology and to provide evidence for PET imaging as a guiding biomarker in nearly all areas of cancer treatment.

Overexpression of prostate specific membrane antigen by canine hemangiosarcoma cells provides opportunity for the molecular detection of disease burdens within hemorrhagic body cavity effusions

Background

Canine hemangiosarcoma (cHSA) is a highly metastatic mesenchymal cancer that disseminates by hematogenous and direct implantation routes. Therapies for cHSA are generally ineffective, in part due to advanced clinical disease stage at the time of diagnosis. The validation of conventional molecular methods for detecting novel biomarkers preferentially expressed by cHSA could lead to more timely diagnosis, earlier therapeutic interventions, and improved outcomes. In humans, prostate-specific membrane antigen (PSMA) is a transmembrane protein overexpressed by prostate carcinoma and tumor-associated endothelium of various solid cancer histologies. Importantly, the preferential overexpression of PSMA by certain cancers has been leveraged for the development of diagnostic molecular imaging reagents and targeted therapeutics. Recently, PSMA has been qualitatively demonstrated to be expressed in cHSA cell lines, however, quantitative PSMA expressions and the potential utility of PSMA transcript identification in biologic fluids to support the presence of microscopic cHSA burden has not been reported. Therefore, this study sought to characterize the differential quantitative expressions of PSMA between cHSA and non-malignant tissues, and to determine the potential diagnostic utility of PCR-generated PSMA amplicons as a surrogate of rare cHSA cells dwelling within peritoneal and pericardial cavities.

Methods

Quantitative gene and protein expressions for PSMA were compared between one normal endothelial and six cHSA cell lines by RT-PCR, western blot analysis, and fluorescent microscopy. Additionally, gene and protein expressions of PSMA in normal canine tissues were characterized. Graded expressions of PSMA were determined in spontaneously-arising cHSA tumor samples and the feasibility of qualitative PCR as a molecular diagnostic to detect PSMA transcripts in whole blood from healthy dogs and hemorrhagic effusions from cHSA-bearing dogs were evaluated.

Results

PSMA gene and protein expressions were elevated (up to 6-fold) in cHSA cells compared with non-malignant endothelium. By immunohistochemistry, protein expressions of PSMA were detectable in all cHSA tissue samples evaluated. As predicted by human protein atlas data, PSMA’s expression was comparably identified at substantial levels in select normal canine tissues including kidney, liver, and intestine. In young healthy pet dogs, PSMA amplicons could not be identified in circulating whole blood yet were detectable in hemorrhagic effusions collected from pet dogs with confirmed cHSA or PSMA-expressing cancer.

Conclusions

PSMA is quantitatively overexpressed in cHSA compared to normal endothelium, but its protein expression is not restricted to only cHSA tumor tissues, as specific visceral organs also substantively express PSMA. Optimized qualitative PCR methods failed to amplify PSMA amplicons sufficiently for visible detection in circulating whole blood derived from healthy young dogs, yet PSMA transcripts were readily identifiable in hemorrhagic effusions collected from pet dogs with histologically confirmed cHSA or PSMA-expressing cancer. While preliminary, findings derived from a limited cohort of normal and diseased pet dogs provocatively raise the potential value of PSMA amplicon detection as an ancillary molecular diagnostic test for supporting the presence of microscopic cHSA disease burden within hemorrhagic body cavity effusions.

Exploration of the diagnostic value and molecular mechanism of miR‑1 in prostate cancer: A study based on meta‑analyses and bioinformatics

Prostate cancer (PCa) remains a principal issue to be addressed in male cancer-associated mortality. Therefore, the present study aimed to examine the clinical value and associated molecular mechanism of microRNA (miR)-1 in PCa. A meta-analysis was conducted to evaluate the diagnosis of miR-1 in PCa via Gene Expression Omnibus and ArrayExpress datasets, The Cancer Genome Atlas miR-1 expression data and published literature. It was identified that expression of miR-1 was significantly downregulated in PCa. Decreased miR-1 expression possessed moderate diagnostic value, with area under the curve, sensitivity, specificity and odds ratio values at 0.73, 0.77, 0.57 and 4.60, respectively. Using bioinformatics methods, it was revealed that a number of pathways, including the ‘androgen receptor signaling pathway’, ‘androgen receptor activity’, ‘transcription factor binding’ and ‘protein processing in the endoplasmic reticulum’, were important in PCa. A total of seven hub genes, including phosphoribosylaminoimidazole carboxylase and phosphoribosylaminoimidazolesuccin ocarboxamide synthase (PAICS), cadherin 1 (CDH1), SRC proto-oncogene, non-receptor tyrosine kinase, twist family bHLH transcription factor 1 (TWIST1), ZW10 interacting kinetochore protein (ZWINT), PCNA clamp associated factor (KIAA0101) and androgen receptor, among which, five (PAICS, CDH1, TWIST1, ZWINT and KIAA0101) were significantly upregulated and negatively correlated with miR-1, were identified as key miR-1 target genes in PCa. Additionally, it was investigated whether miR-1 and its hub genes were associated with clinical features, including age, tumor status, residual tumor, lymph node metastasis, pathological T stage and prostate specific antigen level. Collectively the results suggest that miR-1 may be involved in the progression of PCa, and consequently be a promising diagnostic marker. The ‘androgen receptor signaling pathway’, ‘androgen receptor activity’, ‘transcription factor binding’ and ‘protein processing in the endoplasmic reticulum’ may be crucial interactive pathways in PCa. Furthermore, PAICS, CDH1, TWIST1, ZWINT and KIAA0101 may serve as crucial miR-1 target genes in PCa.

Usefulness of both PET/CT with F18-FDG and whole-body diffusion-weighted imaging in cancer screening: a preliminary report

OBJECTIVE

Positron emission tomography/computed tomography (PET/CT) with fluorodeoxyglucose (F18-FDG) is useful for the detection of malignant lesions, including metastatic lesions, and this technique is widely used in cancer screening. However, this approach may occasionally yield false-positive and false-negative findings. At our PET center, to increase the accuracy of PET/CT, we use PET/CT and whole-body diffusion-weighted imaging (WB-DWI) together. This study aimed to assess the usefulness of this combination.

METHODS

We examined 29 subjects with confirmed diagnosis. All of them had undergone PET/CT and WB-DWI on the same day. Twenty-seven of them also underwent ultrasonography, blood testing, and upper gastrointestinal series on the same day and two fecal occult blood tests on another day. WB-DWI was performed on a 1.5-T MRI unit with a b value of 0 and 800 or 1000 s/mm². For all 29 cases, PET/CT and WB-DWI were classified to be positive or negative, and the diagnostic ability was calculated for each modality.

RESULTS

Among the 29 subjects, 17 had malignant tumors and 12 had benign tumors or no abnormalities. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of PET/CT were 65%, 25%, 55%, 33%, and 48%, respectively; while the corresponding values for WB-DWI were 59%, 100%, 100%, 63%, and 76%, respectively. By considering the result to be negative when PET/CT findings were positive but WB-DWI findings were negative, specificity increased from 25 to 100%, and accuracy increased from 48 to 76%. On the other hand, by considering the result to be positive when the findings of either PET/CT or WB-DWI were positive, sensitivity increased from 65 to 76%, and accuracy increased from 48 to 55%.

CONCLUSIONS

Our results suggest that using both PET/CT and WB-DWI together can increase accuracy in cancer screening. However, this approach was not able to detect malignant lesions in some cases, indicating that there were limitations with imaging certain organs. Therefore, it is important to further understand the features of PET/CT and WB-DWI and use them appropriately for each organ. Additionally, given that the study sample was relatively small, further research is needed to validate these findings.

68Ga-PSMA PET/CT and PET/MRI in high-risk prostate cancer patients

Treatment of high-risk prostate cancer (HRPCa) is challenging. Local staging and metastatic evaluation are important for the patient management. Recently, prostate-specific membrane antigen (PSMA)-based imaging modalities such as PSMA PET/CT and PET/MRI have received significant attention for detection of recurrent prostate cancer sites with elevated prostate-specific antigen levels, after therapy. Current evidence suggests that these imaging modalities may also have a role for the management of patients with HRPCa. In this review, we discuss PSMA-based imaging modalities in the management of patients with HRPCa.

Gastric Metastasis of Prostate Cancer as an Unusual Presentation Using 68Ga-Prostate-Specific Membrane Antigen PET/CT

A 79-year-old man with prostate cancer underwent Ga prostate-specific membrane antigen (Ga-PSMA) dual-time-point PET/CT scan to evaluate tumor activity due to early satiety, unquantified weight loss, and elevation of prostate-specific antigen (PSA), demonstrating thickening of the gastric wall with intense tracer uptake. The immunohistochemistry of gastric biopsy showed CDX2 and CK20: negative; CK7, focal positive; PSA, positive, which confirmed metastatic disease. Metastatic disease was also found in bones, right lung, and retroperitoneal and pelvic lymphadenopathies.

Non-invasive Early Response Monitoring of Nanoparticle-assisted Photothermal Cancer Therapy Using 18F-FDG, 18F-FLT, and 18F-FET PET/CT Imaging

Rationale: Since its first implementation nanoparticle-assisted photothermal cancer therapy has been studied extensively, although mainly with focus on optimal nanoparticle design. However, development of efficient treatment protocols, as well as reliable and early evaluation tools in vivo, are needed to push the therapy towards clinical translation. Positron emission tomography (PET) is a non-invasive imaging technique that is currently finding extensive use for early evaluation of cancer therapies; an approach that has become of increasing interest due to its great potential for personalized medicine.

Methods: In this study, we performed PET imaging to evaluate the treatment response two days after nanoparticle-assisted photothermal cancer therapy in tumor-bearing mice. We used three different tracers; 2′-deoxy-2′-¹⁸F-fluoro-D-glucose (¹⁸F-FDG), 3′-deoxy-3′-¹⁸F-fluorothymidine (¹⁸F-FLT), and O-(2'-¹⁸F-fluoroethyl)-L-tyrosine (¹⁸F-FET) to image and measure treatment induced changes in glucose uptake, cell proliferation, and amino acid transport, respectively. After therapy, tumor growth was monitored longitudinally until endpoint was reached.

Results: We found that nanoparticle-assisted photothermal therapy overall inhibited tumor growth and prolonged survival. All three PET tracers had a significant decrease in tumor uptake two days after therapy and these changes correlated with future tumor growth, with ¹⁸F-FDG having the most predictive value in this tumor model.

Conclusion: This study shows that ¹⁸F-FDG, ¹⁸F-FLT, and ¹⁸F-FET are all robust markers for the treatment response of photothermal therapy, and demonstrate that PET imaging can be used for stratification and optimization of the therapy. Furthermore, having a selection of PET tracers that can reliably measure treatment response is highly valuable as the individual tracer might be excluded in certain applications where physiological processes limit their contrast to background.