PET and PET/CT with radiolabeled choline in prostate cancer: a critical reappraisal of 20 years of clinical studies

Clinical considerations for sexual and gender minorities with prostate cancer

At every stage of the cancer continuum, the management of sexual and gender minorities with prostate cancer requires a thoughtful and multidisciplinary approach. For example, it is important to recognize that receptive anal intercourse, common among sexual minority men-i.e. gay and bisexual men-can potentially elevate prostate-specific antigen (PSA) leading to overdiagnosis and overtreatment. Additionally, it is important to understand that sexual minority men with prostate cancer might engage in insertive and/or receptive anal intercourse, as opposed to insertive vaginal intercourse, requiring a treatment conversation that expands beyond the usual discussion of sexual health in prostate cancer patients. For gender minorities-i.e. transgender women or trans feminine individuals (those recorded male at birth with feminine gender identities)-it is important to consider gender affirming hormones and pelvic surgeries as they can cause diagnostic and treatment challenges, including PSA suppression, more aggressive disease, and anatomical changes. Furthermore, it is essential to recognize that gender minorities are a diverse cohort and may or may not be on gender affirming hormone therapy and may or may not have received or intend to receive pelvic affirming surgery. In this seminar article, we highlight considerations for personalized management of prostate cancer in sexual and gender minorities to improve care for this understudied cohort and enhance health equity.

Comparison of quantitative parameters and radiomic features as inputs into machine learning models to predict the Gleason score of prostate cancer lesions

INTRODUCTION

The classification of prostate cancer (PCa) lesions using Prostate Imaging Reporting and Data System (PI-RADS) suffers from poor inter-reader agreement. This study compared quantitative parameters or radiomic features from multiparametric magnetic resonance imaging (mpMRI) or positron emission tomography (PET), as inputs into machine learning (ML) to predict the Gleason scores (GS) of detected lesions for improved PCa lesion classification.

METHODS

20 biopsy-confirmed PCa subjects underwent imaging before radical prostatectomy. A pathologist assigned GS from tumour tissue. Two radiologists and one nuclear medicine physician delineated the lesions on the mpMR and PET images, yielding 45 lesion inputs. Seven quantitative parameters were extracted from the lesions, namely T2-weighted (T2w) image intensity, apparent diffusion coefficient (ADC), transfer constant (K^TRANS), efflux rate constant (K_ep), and extracellular volume ratio (V_e) from mpMR images, and SUV_mean and SUV_max from PET images. Eight radiomic features were selected out of 109 radiomic features from T2w, ADC and PET images. Quantitative parameters or radiomic features, with risk factors of age, prostate-specific antigen (PSA), PSA density and volume, of 45 different lesion inputs were input in different combinations into four ML models - Decision Tree (DT), Support Vector Machine (SVM), k-Nearest-Neighbour (kNN), Ensembles model (EM).

RESULTS

SUV_max yielded the highest accuracy in discriminating detected lesions. Among the 4 ML models, kNN yielded the highest accuracies of 0.929 using either quantitative parameters or radiomic features with risk factors as input.

CONCLUSIONS

ML models' performance is dependent on the input combinations and risk factors further improve ML classification accuracy.

Positron emission tomography molecular imaging-based cancer phenotyping

During the past several decades, numerous studies have provided insights into biological characteristics of cancer cells and identified various hallmarks of cancer acquired in the tumorigenic processes. However, it is still challenging to image these distinctive traits of cancer to facilitate the management of patients in clinical settings. The rapidly evolving field of positron emission tomography (PET) imaging has provided opportunities to investigate cancer's biological characteristics in vivo. This article reviews the current status of PET imaging on characterizing hallmarks of cancer and discusses the future directions of PET imaging strategies facilitating in vivo cancer phenotyping.

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.

Beyond the Prognostic Value of 2-[18F]FDG PET/CT in Prostate Cancer: A Case Series and Literature Review Focusing on the Diagnostic Value and Impact on Patient Management

The role of 2-deoxy-2-[¹⁸F]fluoro-D-glucose Positron Emission Tomography/Computed Tomography (FDG PET/CT) in the management of prostate cancer (PCa) patients is increasingly recognised. However, its clinical role is still controversial. Many published studies showed that FDG PET/CT might have a prognostic value in the metastatic castration-resistant phase of the disease, but its role in other settings of PCa and, more importantly, its impact on final clinical management remains to be further investigated. We describe a series of six representative clinical cases of PCa in different clinical settings, but all characterised by a measurable clinical impact of FDG PET/CT on the patients’ management. Starting from their clinical history, we report a concise narrative literature review on the advantages and limitations of FDG PET/CT beyond its prognostic value in PCa. What emerges is that in selected cases, this imaging technique may represent a useful tool in managing PCa patients. However, in the absence of dedicated studies to define the optimal clinical setting of its application, no standard recommendations on its use in PCa patients can be made.

Impact of pelvic dynamic acquisition on final reading of 18 F-Fluorocholine positron emission tomography in patients with prostate adenocarcinoma: True need or unnecessary burden?

INTRODUCTION

Despite the increasing use of ¹⁸ F-fluorocholine (¹⁸ F-FCH) positron emission tomography (PET) in patients with prostate cancer, the acquisition protocol remains debated. We have evaluated the influence of the pelvic dynamic phase on the final reading of whole-body ¹⁸ F-FCH PET, to assess the need for a two-stage protocol. Reading the physician's experience and patient's previous treatment profile was also considered as potential influencing factors on final PET interpretation.

METHODS

All ¹⁸ F-FCH PET/CT performed from January 2018 to September 2019 in patients with prostate cancer and including a pelvic dynamic phase followed by a delayed whole-body acquisition were retrospectively retrieved. PET/CT were analysed by one expert nuclear medicine physician and one resident. The whole-body scan was analysed blinded (first reading) and nonblinded from the results of the dynamic phase.

RESULTS

221 consecutive PET/CT were selected from 201 patients previously treated by radical prostatectomy (n = 31), pelvic radiation therapy (n = 60), or both (n = 94). 24 patients had no previous treatments, and 12 benefited from other focal treatments. In the whole population, dynamic acquisition modified final interpretation of 32/221 scans (14.5%) for residents, 26 (11.8%) for experts and 19 (8.6%) for consensual reading. No influence of previous treatments was found. The availability of a dynamic phase would have been responsible for treatment modification in 5/221 scans (2.3%). Considering only the prostate bed, dynamic acquisition modified the final interpretation in 7/125 (5.6%) studies (consensual reading) from patients with previous prostatic surgery and 4/84 (4.8%) scans from patients without a history of prostatic surgical intervention. No significant influence of dynamic acquisition was found on the final PET interpretation on prostate lodge accordingly to previous prostatic surgery.

CONCLUSION

The dynamic phase changes the interpretation of ¹⁸ F-FCH PET in about 9% of cases and the therapeutic strategy in <3% of patients. The influence of the early phase reduces with physician experience. Patient's treatment profile does not appear to have a significant influence on the variability of interpretation, also including the prostate bed.

The Evolving Role of 18F-FDG PET/CT in Diagnosis and Prognosis Prediction in Progressive Prostate Cancer

Positron emission tomography/computed tomography (PET/CT) is widely used in prostate cancer to evaluate the localized tumor burden and detect symptomatic metastatic lesions early. ¹⁸F-FDG is the most used tracer for oncologic imaging, but it has limitations in detecting early-stage prostate cancer. ⁶⁸Ga-PSMA is a new tracer that has high specificity and sensibility in detecting local and metastatic tumors. But with the progression of prostate cancer, the enhancement of glucose metabolism in progressive prostate cancer provides a chance for ¹⁸F-FDG. This review focuses on PET/CT in the detection and prognosis of prostate cancer, summarizing the literature on ¹⁸F-FDG and ⁶⁸Ga-PSMA in prostate cancer and highlighting that ¹⁸F-FDG has advantages in detecting local recurrence, visceral and lymph node metastases compared to ⁶⁸Ga-PSMA in partial progressive prostate cancer and castration-resistant prostate cancer patients. We emphasize ¹⁸F-FDG PET/CT can compensate for the weakness of ⁶⁸Ga-PSMA PET/CT in progressive prostate cancer.

Prostate Cancer Diagnostic Algorithm as a "Road Map" from the First Stratification of the Patient to the Final Treatment Decision

The diagnostics of prostate cancer are currently based on three pillars: prostate biomarker panel, imaging techniques, and histological verification. This paper presents a diagnostic algorithm that can serve as a "road map": from initial patient stratification to the final decision regarding treatment. The algorithm is based on a review of the current literature combined with our own experience. Diagnostic algorithms are a feature of an advanced healthcare system in which all steps are consciously coordinated and optimized to ensure the proper individualization of the treatment process. The prostate cancer diagnostic algorithm was created using the prostate specific antigen and in particular the Prostate Health Index in the first line of patient stratification. It then continued on the diagnostic pathway via imaging techniques, biopsy, or active surveillance, and then on to the treatment decision itself. In conclusion, the prostate cancer diagnostic algorithm presented here is a functional tool for initial patient stratification, comprehensive staging, and aggressiveness assessment. Above all, emphasis is placed on the use of the Prostate Health Index (PHI) in the first stratification of the patients as a predictor of aggressiveness and clinical stage of prostrate cancer (PCa). The inclusion of PHI in the algorithm significantly increases the accuracy and speed of the diagnostic procedure and allows to choose the optimal pathway just from the beginning. The use of advanced diagnostic techniques allows us to move towards to a more advanced level of cancer care. This diagnostics algorithm has become a standard of care in our hospital. The algorithm is continuously validated and modified based on our results.

Will 18F-fluorocholine PET/CT replace other methods of preoperative parathyroid imaging?

INTRODUCTION

Primary hyperparathyroidism (PHPT) is a common endocrine disorder usually due to hyperfunctioning parathyroid glands (HPs). Surgical removal of the HPs is the main treatment for PHPT, making the correct detection and localization of HPs crucial to guiding targeted and minimally invasive surgical treatment in patients with PHPT. To date, different imaging methods have been used to detect and localize HPs, including radiology, nuclear medicine, and hybrid techniques.

METHODS

The present work discusses the role and value of different imaging methods in PHPT and, particularly, evaluates the potential role of ¹⁸F-fluorcholine PET/CT as a "one-stop-shop" method for preoperative parathyroid localization in patients with PHPT.

DISCUSSION

Cervical ultrasound (US) and parathyroid scintigraphy using ^99mTc-MIBI are the most commonly employed methods in clinical practice. More recently, four-dimensional computed tomography (4D CT) and positron emission tomography (PET) with radiolabeled choline have emerged as useful alternatives in cases of negative or discordant findings from first-line imaging methods.

CONCLUSIONS

Due to the excellent diagnostic performance of radiolabeled choline PET/CT and the low radiation burden, this technique seems to be an ideal candidate to substitute current imaging procedures including US, MIBI scintigraphy, 4D CT and MRI and perform a fast and reliable "one-stop-shop" preoperative localization of HP in patients with PHPT, including challenging cases of postoperative persistent/recurrent disease.

Standardization of acquisition protocols using PET/CT with 18F-Choline in prostate cancer

AIM

To standardize acquisition protocols for ¹⁸F-Choline PET/CT to prevent from urine interference, to determine the best time point for the whole-body study, and to assess whether "dual point" acquisition allows for differentiating malignant vs. benign lesions.

METHODS

One hundred consecutive patients with prostate cancer were prospectively studied. Immediately after ¹⁸F-Choline injection, a pelvis study was acquired, and a whole-body was subsequently obtained 1 and 2 hours p.i. Mean SUVmax was obtained in regions and for every sequential imaging. Mean analysis (χ²) and SUV percentage change (2/1 hours; 1 hours/0 min) were obtained. Metabolic pattern dynamics were assessed: accumulative vs. clearance. Patient follow-up after therapy and directed classification whenever ethically possible were performed.

RESULTS

Fifty-three prostate foci, without disturbing urinary activity was ever found on early images. Accumulative pattern in 42, with percentage increase was: 0 min/1 hour: +16.7% (χ²0.94); 1/2 hours: +10,0% (χ² 0.83). Clearance pattern in 11, with percentage decrease: 0 min/1 hour: -21.4% (χ²0.91): -7.7% (χ²0.85), corresponding in 7 to initial staging and in 4 post-radiotherapy biochemical recurrence. Every infradiaphragmatic uptake (n: 24) showed accumulative pattern, with percentage increase of +9.1% (χ²0.97), all of them depicted on early imaging. As for 12 supradiaphragmantic uptake, 8 of them showed clearance pattern with percentage decrease: -13.0% (χ²0.95). Accumulative pattern showed in 4 of them with percentage increase +13.0% (χ² 0.96), thus being assessed as invasive/malignant. Every bone uptake (n: 18) showed accumulative pattern, with percentage increase: +17.1% (χ²0.95), all of them depicted on 1 hour imaging.

CONCLUSIONS

As for prostate assessment is concerned, dual point at 0 min/1 hour proved to be the best procedure. As for supradiaphragmatic lymph-nodes detection, dual point with 1/2 hours performed best. As for infradiaphragmatic and bone involvement, as well as for inconclusive findings, the 2 hour imaging increased our diagnostic confidence.

Nodal recurrence patterns on PET/CT after RTOG-based nodal radiotherapy for prostate cancer

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Recurrence patterns on PET/CT after RT for PC_N+ were correlated with nodal fields.

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In-field nodal recurrences were uncommon.

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Out-field nodal recurrences occurred mostly just above the elective nodal field.

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Expanding elective fields to the aorta bifurcation may prolong disease-free survival.

Purpose

Biochemical failure after external beam radiotherapy (RT) for node-positive prostate cancer (PC_N+) frequently involves nodal recurrences, in most cases out of field. This raises the question if current RTOG-based elective nodal fields can still be considered optimal. Modern diagnostic tools like PSMA PET/CT and choline PET/CT can visualize nodal recurrences with unprecedented accuracy. We evaluated recurrence patterns on PET/CT after RT for PC_N+, with the aim to explore options for improved nodal target definition.

Methods and materials

Data of all patients treated with curative intent EBRT for PC_N+ in NKI-AVL from 2008 to 2018 were retrospectively reviewed. EBRT comprised 70 Gy to the prostate or 66–70 Gy to the prostate bed, 60 Gy to involved nodes, and 52,5–56 Gy (46 Gy EQD2) to RTOG-based elective nodal fields, in 35 fractions. Locations of recurrences on PET/CT were noted, and nodal locations were correlated with the applied EBRT fields.

Results

42 patients received PSMA (28) or choline (14) PET/CT at biochemical recurrence. 35 patients (83%) had a positive scan. At their first positive scan 17 patients had nodal metastasis, in some cases together with a local recurrence or distant disease. In-field nodal recurrences were uncommon (n = 3). Out-field nodal recurrences occurred more frequently (n = 14), with the majority (n = 12) just above the elective nodal field. These nodes were the single area of detectable failure in 6 patients (14%).

Conclusions

Current RT with RTOG-based nodal fields for PC_N+ provides good in-field tumour control, but frequent out-field nodal recurrences suggest missed microscopic locations. Expanding elective fields to include the aorta bifurcation may prolong recurrence-free survival. Future research must address whether the potential benefits of this strategy outbalance additional toxicity.

Artificial intelligence-based versus manual assessment of prostate cancer in the prostate gland: a method comparison study

AIM

To test the feasibility of a fully automated artificial intelligence-based method providing PET measures of prostate cancer (PCa).

METHODS

A convolutional neural network (CNN) was trained for automated measurements in ¹⁸ F-choline (FCH) PET/CT scans obtained prior to radical prostatectomy (RP) in 45 patients with newly diagnosed PCa. Automated values were obtained for prostate volume, maximal standardized uptake value (SUV_max ), mean standardized uptake value of voxels considered abnormal (SUV_mean ) and volume of abnormal voxels (Vol_abn ). The product SUV_mean  × Vol_abn was calculated to reflect total lesion uptake (TLU). Corresponding manual measurements were performed. CNN-estimated data were compared with the weighted surgically removed tissue specimens and manually derived data and related to clinical parameters assuming that 1 g ≈ 1 ml of tissue.

RESULTS

The mean (range) weight of the prostate specimens was 44 g (20-109), while CNN-estimated volume was 62 ml (31-108) with a mean difference of 13·5 g or ml (95% CI: 9·78-17·32). The two measures were significantly correlated (r = 0·77, P<0·001). Mean differences (95% CI) between CNN-based and manually derived PET measures of SUVmax, SUVmean, Vol_abn (ml) and TLU were 0·37 (-0·01 to 0·75), -0·08 (-0·30 to 0·14), 1·40 (-2·26 to 5·06) and 9·61 (-3·95 to 23·17), respectively. PET findings Vol_abn and TLU correlated with PSA (P<0·05), but not with Gleason score or stage.

CONCLUSION

Automated CNN segmentation provided in seconds volume and simple PET measures similar to manually derived ones. Further studies on automated CNN segmentation with newer tracers such as radiolabelled prostate-specific membrane antigen are warranted.

Development of a thin layer chromatography method for plasma correction of [18F]fluorocholine metabolites in positron emission tomography quantification studies in humans

INTRODUCTION

After its intravenous injection, [¹⁸F]fluorocholine is oxidized by choline-oxidase into its main plasma metabolite, [¹⁸F]fluorobetaine. If PET kinetic modeling quantification of [¹⁸F]fluorocholine uptake is intended, the plasma input time-activity-curve of the parent tracer must be obtained, i.e., the fraction of the total plasma radioactivity corresponding to the nonmetabolized [¹⁸F]fluorocholine at each time has to be known. Hence our aim was to develop an easy-routine Thin-Layer-Chromatography (TLC) method to separate and quantify the relative fractions of [¹⁸F]fluorocholine and [¹⁸F]fluorobetaine as a function of time during PET imaging in humans.

METHODS

First, we tested several combinations of solvents systems and layers to select the one showing the best resolution on non-radioactive standards. Thereafter, [¹⁸F]fluorobetaine was obtained through chemical oxidation of an [¹⁸F]fluorocholine sample at diferent incubation times and we applied the selected TLC-system to aliquots of this oxidation solution, both in a saline and in human deproteinized plasma matrices. The plates were detected by a radio-TLC-scanner. This TLC-system was finally applied to arterial plasma samples from 9 patients with high-grade-glioma undergoing brain PET imaging and a parent fraction curve was obtained in each of them.

RESULTS

A TLC-system based on Silica-Gel-60//MeOH-NH₃ was selected from the choline/betaine non-radioactive standards assay. Radiochromatograms of [¹⁸F]fluorocholine oxidation solution yielded two separated and well-defined peaks, Rf = 0,03 ([¹⁸F]fluorocholine) and Rf = 0.78 (¹⁸F]fluorobetaine) consistent with those observed on non-radioactive standards. During the oxidation, the [¹⁸F]fluorocholine radioactivity peak decreased progressively at several incubation times, while the other peak ([¹⁸F]fluorobetaine) increased accordingly. The mean values of the parent fraction of [¹⁸F]fluorocholine of the 9 patients studied (mean+/-SD) were 94% ± 6%, 58% ± 15%, 43% ± 10%, 39% ± 6% and 37% ± 6% at 2.8 min, 5.8 min, 8.8 min, 11.7 min and 14.7 min post-injection, respectively.

CONCLUSIONS

We have developed a TLC-system, easy to perform in a standard radiopharmacy unit, that enables the metabolite correction of arterial input function of [¹⁸F]fluorocholine in patients undergoing PET oncologic quantitative imaging.

Characteristics, trend, and methodological quality of systematic reviews and meta-analyses in nuclear medicine: A bibliometric analysis of studies published between 2005 and 2016

To evaluate the characteristics, trend, and quality of systematic reviews and meta-analyses in nuclear medicine.We performed a PubMed search to identify systematic reviews and meta-analyses published between 2005 and 2016 in the field of nuclear medicine. The following data were extracted: journal name, impact factor, type of study, topics with cancer type, imaging modalities, authors (number, country, affiliation, presence of nuclear medicine specialists and statisticians, discordance between the first and corresponding authors), funding, methodological quality, methods used for quality assessment, and statistical methods.We included 185 nuclear medicine articles. Meta-analyses (n = 164; 88.6%) were published about 7 times more frequently than systematic reviews. Oncology was the most commonly studied topic (n = 125, 67.6%). The first authors were most frequently located in China (n = 73; 39.5%). PET was the most commonly used modality (n = 150; 81.1%). Both the number of authors and the ratio of discordance between the first and corresponding authors tended to progressively increase over time.The mean AMSTAR score increased over time (5.77 in 2005-2008, 6.71 in 2009-2012, and 7.44 in 2013-2016). The proportion of articles with quality assessment increased significantly (20/26 in 2005-2008, 54/65 in 2009-2012, and 79/94 in 2013-2016). The most commonly used assessment tool was quality assessment of diagnostic accuracy studies (n = 85; 54.9%).The number and quality of systematic reviews and meta-analyses in nuclear medicine have significantly increased over the review period; however, the quality of these articles varies. Efforts to overcome specific weaknesses of the methodologies can provide opportunities for quality improvement.

Role of 18F-Choline Positron Emission Tomography/Computed Tomography to Detect Structural Relapse in High-Risk Differentiated Thyroid Cancer Patients

BACKGROUND

This study aimed to evaluate the role of ¹⁸F-choline (¹⁸F-FCH) positron emission tomography (PET)/computed tomography (CT) in high-risk differentiated thyroid cancer (DTC) patients with suspected relapse. It also compared ¹⁸F-FCH-PET/CT results with those of fludeoxyglucose (¹⁸F-FDG)-PET/CT and evaluated the additional diagnostic value and clinical impact of the combined use of these two tracers. Finally, it assessed the association between the clinical, biochemical, and histological parameters and ¹⁸F-FCH-PET/CT and ¹⁸F-FDG-PET/CT results.

METHODS

The study prospectively enrolled high-risk DTC patients treated with thyroidectomy and radioactive iodine therapy and presenting high/increasing thyroglobulin levels under thyrotropin suppression, negative/inconclusive neck ultrasound, and negative ¹³¹I whole-body scan. All patients underwent ¹⁸F-FDG-PET/CT and ¹⁸F-FCH-PET/CT within 30 days of each other. Experienced nuclear medicine physicians examined the images of both procedures, and an integrated analysis of the two PET/CT modalities was also conducted. For each modality, a patient-based analysis (PBA) and lesion-based-analysis (LBA) was performed. On PBA, sensitivity, specificity, negative predictive value, positive predictive value, and accuracy were calculated. On LBA, only sensitivity was calculated. The standard of reference was based on clinical, imaging, and histological data.

RESULTS

Twenty-five high-risk DTC patients were included; DTC relapse/persistence was confirmed in 23 patients. On PBA, ¹⁸F-FDG-PET/CT, ¹⁸F-FCH-PET/CT, and the integrated evaluation of the two imaging modalities showed the following rates: sensitivity, specificity, negative predictive value, positive predictive value, and accuracy were 69.6%, 100%, 22.2%, 100%, and 72% versus 56.5%, 100%, 16.7%, 100%, and 60% versus 82.6%, 100%, 33.3%, 100%, and 84%, respectively. When compared with ¹⁸F-FDG-PET/CT, the integrated analysis of these two imaging procedures changed the clinical management in 4/23 (17%) patients. On LBA, the sensitivity rates of ¹⁸F-FDG-PET/CT, ¹⁸F-FCH-PET/CT, and the combined evaluation of the two modalities were 58.7%, 38.1%, and 66.7%, respectively; when only lymph node involvement was considered, the rates were 56.3%, 53.1%, and 68.8%, respectively. Serum thyroglobulin doubling time (Tg-DT) <12 months was significantly associated with positive 18F-FCH-PET/CT. A trend toward a significant association was also found between positive 18F-FDG-PET/CT and both Tg-DT <12 months and DTC aggressive subtypes.

CONCLUSION

¹⁸F-FCH-PET/CT may add important information during the follow-up of high-risk DTC patients. ¹⁸F-FCH-PET/CT may be considered a useful complementary tool in patients affected by non-aggressive DTC subtypes, with Tg-DT <12 months, high risk of lymph node spreading, and negative or doubtful ¹⁸F-FDG-PET/CT.

Impact of penalizing factor in a block-sequential regularized expectation maximization reconstruction algorithm for 18F-fluorocholine PET-CT regarding image quality and interpretation

BACKGROUND

Recently, the block-sequential regularized expectation maximization (BSREM) reconstruction algorithm was commercially introduced (Q.Clear, GE Healthcare, Milwaukee, WI, USA). However, the combination of noise-penalizing factor (β), acquisition time, and administered activity for optimal image quality has not been established for ¹⁸F-fluorocholine (FCH). The aim was to compare image quality and diagnostic performance of different reconstruction protocols for patients with prostate cancer being examined with ¹⁸F-FCH on a silicon photomultiplier-based PET-CT. Thirteen patients were included, injected with 4 MBq/kg, and images were acquired after 1 h. Images were reconstructed with frame durations of 1.0, 1.5, and 2.0 min using β of 150, 200, 300, 400, 500, and 550. An ordered subset expectation maximization (OSEM) reconstruction with a frame duration of 2.0 min was used for comparison. Images were quantitatively analyzed regarding standardized uptake values (SUV) in metastatic lymph nodes, local background, and muscle to obtain contrast-to-noise ratios (CNR) as well as the noise level in muscle. Images were analyzed regarding image quality and number of metastatic lymph nodes by two nuclear medicine physicians.

RESULTS

The highest median CNR was found for BSREM with a β of 300 and a frame duration of 2.0 min. The OSEM reconstruction had the lowest median CNR. Both the noise level and lesion SUV_max decreased with increasing β. For a frame duration of 1.5 min, the median quality score was highest for β 400-500, and for a frame duration of 2.0 min the score was highest for β 300-500. There was no statistically significant difference in the number of suspected lymph node metastases between the different image series for one of the physicians, and for the other physician the number of lymph nodes differed only for one combination of image series.

CONCLUSIONS

To achieve acceptable image quality at 4 MBq/kg ¹⁸F-FCH, we propose using a β of 400-550 with a frame duration of 1.5 min. The lower β should be used if a high CNR is desired and the higher if a low noise level is important.

The Impact of Positron Emission Tomography with 18F-Fluciclovine on the Treatment of Biochemical Recurrence of Prostate Cancer: Results from the LOCATE Trial

PURPOSE

The prospective, multicenter LOCATE (F Fluciclovine [FACBC] PET/CT in Patients with Rising PSA after Initial Prostate Cancer Treatment) trial assessed the impact of positron emission tomography/computerized tomography with F-fluciclovine on treatment plans in patients with biochemical recurrence of prostate cancer after primary therapy with curative intent.

MATERIALS AND METHODS

Men who had undergone curative intent treatment of histologically confirmed prostate cancer but who were suspected to have recurrence based on rising prostate specific antigen levels were enrolled prospectively. Each man had negative or equivocal findings on standard of care imaging. F-fluciclovine positron emission tomography/computerized tomography was performed according to standardized protocols. Treating physicians completed a questionnaire regarding the patient treatment plan before and after scanning, recording changes to the treatment modality (eg salvage radiotherapy to systemic androgen deprivation therapy) as major and changes in a modality (eg modified radiotherapy fields) as other.

RESULTS

Between June 2016 and May 2017, 213 evaluable patients with a median age of 67 years and median prostate specific antigen 1.00 ng/ml were enrolled in study. F-fluciclovine avid lesions were detected in 122 of the 213 patients (57%). Overall 126 of the 213 patients (59%) had a change in management after the scan, which were major in 98 of 126 (78%) and in 88 (70%) were informed by positive positron emission tomography/computerized tomography findings. The most frequent major changes were from salvage or noncurative systemic therapy to watchful waiting (32 of 126 cases or 25%), from noncurative systemic therapy to salvage therapy (30 of 126 or 24%) and from salvage therapy to noncurative systemic therapy (11 of 126 or 9%).

CONCLUSIONS

F-fluciclovine positron emission tomography/computerized tomography detected 1 or more recurrence sites in the majority of men with biochemical recurrence, frequently resulting in major changes to management plans. Future studies will be planned to determine whether a management change leads to improved outcomes.

11C-choline PET/CT predicts survival in prostate cancer patients with PSA < 1 NG/ml

PURPOSE

The main drawback of ¹¹C-choline PET/CT for restaging prostate cancer (PCa) patients with biochemical failure is the relatively low positive detection rate for prostate specific antigen (PSA) < 1 ng/ml. This study assessed whether ¹¹C-choline PET/CT predicts survival in PCa patients with PSA < 1 ng/ml.

METHODS

This retrospective study included 210 PCa patients treated with radical prostatectomy who underwent ¹¹C-choline PET/CT from December 1, 2004 to July 31, 2007 due to biochemical failure. PCa-specific survival was estimated using Kaplan-Meier curves. Cox regression analysis was used to evaluate the association between clinicopathologic variables and PCa-specific survival. PCa-specific survival was computed as the interval from radical prostatectomy to PCa-specific death.

RESULTS

Median follow-up after radical prostatectomy was 6.9 years (95% confidence interval, CI, 2.0-14.5 years). ¹¹C-choline PET/CT was positive in 20.5% of patients. Median PCa-specific survival was 13.4 years (95% CI, 9.9-16.8 years) in patients with positive ¹¹C-choline PET/CT, and it was not achieved in patients with negative ¹¹C-choline PET/CT (log-rank, chi-square = 15.0, P < 0.001). Ten-year survival probabilities for patients with negative ¹¹C-choline PET/CT and for patients with positive ¹¹C-choline PET/CT were 86.0% (95% CI: 80.7%-91.3%) and 63.6% (95% CI: 54.5-72.7%). At multivariate analysis, only ¹¹C-choline PET/CT significantly predicted PCa-specific survival (hazard ratio = 2.54, 95% CI, 1.05-6.13, P = 0.038). Patients with pathological ¹¹C-choline uptake in the prostatic bed or in pelvic lymph nodes had longer PCa-specific survival in comparison to patients with pathological tracer uptake in the skeleton (log-rank: chi-square = 27.4, P < 0.001).

CONCLUSION

Despite the relatively low positive detection rate for PSA < 1 ng/ml, positive ¹¹C-choline PET/CT predicts PCa-specific survival in this low PSA range. As long as more sensitive radiotracers, such as ⁶⁸Ga-PSMA-11, do not become more widely available, these results might support a broader use of radiolabeled choline in restaging PCa for PSA < 1 ng/ml.

Oligometastatic Prostate Cancer: A Shrinking Subset or an Opportunity for Cure?

Oligometastatic prostate cancer (OMPC), generally defined by presence of five or fewer metastatic sites on imaging, represents a transitional state between localized and widespread metastatic disease and encompasses a wide spectrum of disease biologies and clinical behaviors. A collaborative effort is ongoing to determine the genomics of OMPC. The prevalence of OMPC varies significantly in the literature and is likely to change further as substantial improvements in imaging improve our ability to reclassify a subset of patients with biochemical recurrence by conventional imaging as OMPC and another subset from OMPC to polymetastatic disease. The mainstay of OMPC treatment remains systemic therapy, either with androgen-deprivation therapy (ADT) alone or in combination with other agents (docetaxel, abiraterone, etc.). Focal therapies, including resection or radiotherapy (RT), to the primary tumor have demonstrated an improvement in outcomes, including failure-free survival in several retrospective studies. RT to the prostate has specifically demonstrated an overall survival (OS) advantage in patients with low-volume disease in a clinical trial. Improvement in outcomes has been observed with focal therapies for retroperitoneal and more distant metastatic sites in retrospective studies. Advancements in our understanding of the biology, imaging modalities, and treatments may allow for aggressive multimodality therapies in an effort to obtain deeper responses and, potentially, cures for selected patients with OMPC with favorable clinicopathologic characteristics. Participation in clinical trials or institutional registries is strongly encouraged for patients with OMPC who opt for an aggressive multimodality approach.

Role of 11C-choline PET/CT in radiation therapy planning of patients with prostate cancer

BACKGROUND

In the era of image-guided radiotherapy, PET has become an important tool for tumor delineation in several types of cancer. The aim of this study was to evaluate the effect of this imaging modality in treatment planning of a cohort of patients with prostate cancer eligible for radiotherapy.

METHODS

From September 2011 to January 2016, 135 consecutive patients (median age 69 years, range: 53-89) were referred to our department for radiation therapy with radical intent (n=28), for postoperative adjuvant (n=13) or salvage treatment (n=50), for re-irradiation (n=19), or for radiotherapy on oligometastases (n=25). Before planning the radiotherapy course, patients were submitted to carbon-11-choline PET (Cho-PET) to confirm the indication to radiotherapy and the irradiation volumes.

RESULTS

Among the 135 patients subjected to Cho-PET, the indication to radiotherapy was modified in 66 (48.8%) cases based on the Cho-PET result. In particular, Cho-PET helped to better define the radiotherapy programme in 12 out of 28 (42.8%) patients who were candidates for primary radiation therapy, 33 (52.4%) of 63 patients undergoing adjuvant/salvage radiotherapy, and 21 out of 44 (47.7%) patients with relapsed/metastatic disease. Overall biochemical response is documented by mean and median prostate specific antigen values, which changed from 15.29 to 4.00 ng/ml, respectively, before to mean 4.74 ng/ml and median 0.81 ng/ml after therapy (P=0.05).

CONCLUSION

In our series, Cho-PET had a significant effect on radiotherapy planning of patients affected by prostate cancer, determining a change in management in 48.8% of cases, considering all therapeutic indications.

68Ga-PSMA-PET: added value and future applications in comparison to the current use of choline-PET and mpMRI in the workup of prostate cancer

Positron emission tomography (PET) has been commonly and successfully used, in combination with computed tomography (CT) and more recently magnetic resonance (MRI), in the workup of intermediate or high-risk prostate cancer (PCa). Nowadays, new specific receptor targeted PET tracers in prostate cancer imaging have been introduced; one of the most used is ⁶⁸Ga-PSMA, that evaluates the expression of prostate-specific membrane antigen (PSMA). This tracer has been rapidly taken into account for its better sensitivity and specificity compared to lipid metabolism tracers, such as ¹¹C/¹⁸F labelled fluorocholine. Besides, in the era of theranostics, this tracer is having a useful application not only for imaging but also for therapeutic purposes. The aim of this review article is, in the first part, to give an overview of the main indications and future development of ⁶⁸Ga-PSMA imaging, using PET/CT or PET/MRI, according to the clinical course of the disease and in view of the current use of multiparametric MRI (mpMRI) and choline PET in the management of PCa. In the second part, a brief overview of the promising ¹⁸F-labelled PSMA tracers and the current use of PSMA radionuclide therapy will be provided.

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.

Current status of theranostics in prostate cancer

The aim of this review is to report on the current status of prostate-specific membrane antigen (PSMA)-directed theranostics in prostate cancer (PC) patients. The value of 68Ga-PSMA-directed PET imaging as a diagnostic procedure for primary and recurrent PC as well as the role of evolving PSMA radioligand therapy (PRLT) in castration-resistant (CR)PC is assessed. The most eminent data from mostly retrospective studies currently available on theranostics of prostate cancer are discussed. The current knowledge on 68Ga-PSMA PET/CT implicates that primary staging with PET/CT is meaningful in patients with high-risk PC and that the combination with pelvic multi parametric (mp)MR (or PET/mpMR) reaches the highest impact on patient management. There may be a place for 68Ga-PSMA PET/CT in intermediate-risk PC patients as well, however, only a few data are available at the moment. In secondary staging for local recurrence, 68Ga-PSMA PET/mpMR is superior to PET/CT, whereas for distant recurrence, PET/CT has equivalent results and is faster and cheaper compared to PET/mpMR. 68Ga-PSMA PET/CT is superior to 18F / 11Choline PET/CT in primary staging as well as in secondary staging. In patients with biochemical relapse, PET/CT positivity is directly associated with prostate-specific antigen (PSA) increase and amounts to roughly 50% when PSA is raised to ≤0.5 ng/ml and to ≥90% above 1 ng/ml. Significant clinical results have so far been achieved with the subsequent use of radiolabeled PSMA ligands in the treatment of CRPC. Accumulated activities of 30 to 50 GBq of 177Lu-PSMA ligands seem to be clinically safe with biochemical response and PERCIST/RECIST response in around 75% of patients along with xerostomia in 5-10% of patients as the only notable side effect. On the basis of the current literature, we conclude that PSMA-directed theranostics do have a major clinical impact in diagnosis and therapy of PC patients. We recommend that 68Ga-PSMA PET/CT should be performed in primary staging together with pelvic mpMR in high-risk patients and in all patients for secondary staging, and that PSMA-directed therapy is a potent strategy in CRPC patients when other treatment options have failed. The combination of PSMA-directed therapy with existing therapy modalities (such as 223Ra-chloride or androgen deprivation therapy) has to be explored, and prospective clinical multicenter trials with theranostics are warranted.

Synthesis and evaluation of a novel urea-based 68Ga-complex for imaging PSMA binding in tumor

INTRODUCTION

Prostate specific membrane antigen (PSMA) is a well-established target for diagnostic and therapeutic applications for prostate cancer. It is know that [⁶⁸Ga]PSMA 11 ([⁶⁸Ga]Glu-NH-CO-NH-Lys(Ahx)-HBED-CC) is the most well studied PET imaging agent for detecting over expressed PSMA binding sites of tumors in humans. In an effort to provide new agents with improved characteristics for PET imaging, we report a novel [⁶⁸Ga]-Glu-NH-CO-NH-Lys(Ahx)-linker-HBED-CC conjugate with a novel O-(carboxymethyl)-L-tyrosine, as the linker group.

METHODS

Radiosynthesis was performed by a direct method. In vitro binding and cell internalization of [⁶⁸Ga]10 was investigated in PSMA positive LNCaP cell lines. Biodistribution and MicroPET imaging studies were performed in LNCaP tumor bearing mice.

RESULTS

In vitro binding to LNCaP cells showed that ^natGa labeled O-(carboxymethyl)-L-tyrosine conjugate, [^natGa]10, displayed excellent affinity and specificity (IC₅₀ = 16.5 nM) a value comparable to that of PSMA 11. In vitro cell binding and internalization showed excellent uptake and retention; [⁶⁸Ga]10 displayed significantly higher cellular internalization than [⁶⁸Ga]PSMA 11 (12.5 vs 7.4% ID/10⁶ cells at 1 h). Biodistribution studies in LNCaP tumor-bearing mice exhibited a high specific uptake in PSMA expressing tumors and fast clearance in normal organs (19.7 tumor/blood; 20.7 tumor/muscle at 1 h after iv injection). MicroPET imaging studies in mice confirmed that [⁶⁸Ga]10 displayed excellent uptake and distinctive tumor localization, which was blocked by iv injection of a competing drug, 2-PMPA.

CONCLUSIONS

The preliminary results strongly suggest that [⁶⁸Ga]10 may be promising candidates as a PET imaging radiotracer for detecting PSMA expression in prostate cancer.