Early biochemical relapse after radical prostatectomy: which prostate cancer patients may benefit from a restaging 11C-Choline PET/CT scan before salvage radiation therapy?

"Utility of PET/CT with [18F] F-fluorocholine in assessing the response to antiandrogenic therapy in patients with prostate cancer."

OBJECTIVE

To evaluate the correlation between response assessment measured by PET/CT with [18F] F-fluorocholine (Choline PET/CT) and serum levels of PSA in patients with prostate cancer under antiandrogenic treatment.

METHODOLOGY

A retrospective study included patients with CRPC (castration-resistant prostate cancer) and HSPC (hormone sensitive prostate cancer) treated with enzalutamide, abiraterone, or apalutamide between June 2018 and July 2021, who underwent baseline and a follow-up Choline PET/CT. The difference in maximum SUVmax (ΔSUV) between both studies and the PSA value before and at follow-up were recorded. The response to treatment was compared by PSA vs. PET, assessing their association, agreement, and correlation.

RESULTS

Thirty patients were included (median age 74 years, range 68-78), 12 with CSPC and 18 with CRPC; 22 had nodal disease, and 15 had active bone disease. The average time between pre-treatment and follow-up PET/CT was 11 months (range 3.5-23). Patients with extra-nodal metastatic disease at the beginning of treatment showed a higher correlation between PSA and ΔSUV (OR 4.375). In patients with bone disease at the start of treatment, 80% were classified as non-responders on PET response assessment, while only 40% were non-responders by PSA. The correlation between PET and PSA was mild (Kendall's tau_b 0.26), and the classification into Responders/Non-responders had only slight agreement (Cohen's kappa 0.30).

CONCLUSION

Choline PET/CT shows low concordance with the PSA values obtained during the follow-up of response to anti-androgen therapy, especially in patients with bone involvement.

Impact of Clinical Factors on 18F-Flotufolastat Detection Rates in Men With Recurrent Prostate Cancer: Exploratory Analysis of the Phase 3 SPOTLIGHT Study

Purpose

18F-Flotufolastat (18F-rhPSMA-7.3) is a newly approved prostate-specific membrane antigen targeting radiopharmaceutical for diagnostic imaging of prostate cancer (PCa). SPOTLIGHT (National Clinical Trials 04186845) evaluated 18F-flotufolastat in men with suspected PCa recurrence. Here, we present results of predefined exploratory endpoints from SPOTLIGHT to evaluate the impact of clinical factors on 18F-flotufolastat detection rates (DR).

Methods and Materials

The impact of baseline prostate-specific antigen (PSA), PSA doubling time (PSAdt), and International Society of Urologic Pathology Grade Group (GG) on 18F-flotufolastat DR was evaluated among all SPOTLIGHT patients with an evaluable scan, with DR stratified according to the patients' prior treatment (radical prostatectomy ± radiation therapy [RP] or radiation therapy only [RT]). The patients underwent positron emission tomography 50 to 70 minutes after receiving 18F-flotufolastat (296 MBq IV), and scans were read by 3 blinded central readers, with the majority read representing agreement between ≥2 readers.

Results

In total, 389 men (median PSA: 1.10 ng/mL) were evaluable. By majority read, 18F-flotufolastat identified distant lesions in 39% and 43% of patients treated with prior RP or RT, respectively. The overall DR broadly increased with increasing PSA (<0.2 ng/mL: 33%; ≥10 ng/mL: 100%). Among patients with PSA <1 ng/mL, 68% had positive scans, and 27% had extrapelvic findings. PSAdt was available for 145/389 (37%) patients. PSAdt did not appear to influence 18F-flotufolastat DR (77%-90% across all PSAdt categories). Among patients with prior RP, DR ranged from 70% to 83% across PSAdt categories, and 100% DR was reported for all post-RT patients. In total, 362/389 (93%) patients had baseline GG data. Overall DRs were uniformly high (75%‒95%) across all GG. When stratified by prior treatment, DRs across all GG were 69% to 89% in patients with prior RP and ≥96% in patients with prior RT.

Conclusions

18F-Flotufolastat-positron emission tomography enabled the accurate detection of recurrent PCa lesions across a wide range of PSA, PSAdt, and International Society of Urologic Pathology GG, thus supporting its clinical utility for a broad range of patients with recurrent PCa.

Prostate cancer: nuclear medicine imaging in the biochemical recurrence and in oligometastatic disease

INTRODUCTION

The aim of this article was to offer a comprehensive non-systematic review of the literature about the use of Nuclear Medicine imaging exams for the evaluation of prostate cancer (PCa) in the recurrent setting, with a particular regard to positron emission tomography/computed tomography (PET/CT) imaging.

EVIDENCE ACQUISITION

A comprehensive nonsystematic literature review was performed in March 2024. Literature search was updated until March 2024. The most relevant studies have been summarized, giving priority to registered clinical trials and multicenter collaborations.

EVIDENCE SYNTHESIS

Restaging BCR with advanced Nuclear Medicine Imaging, such as prostate-specific membrane antigen-PET/CT could lead to stage migration and pave the way for additional management strategies, such as stereotactic ablative radiotherapy in patients with low-burden or oligometastatic disease, potentially delaying the need of systemic therapies. While OS benefits of targeting PET/CT positive disease are still lacking, data on progression- and metastasis-free-survival are emerging. Improvements in quality-of-life assessments are already evident.

CONCLUSIONS

PCa is one of the most common malignancy in men. In the last 10 years PCa imaging has become significantly more accurate and is now essential for the definition of the extent of the disease in different phases of its natural history. This opened the road to novel management strategies, especially in the recurrent setting, in which the oligometastatic state is now being explored in several trials regarding the prognostic significance of metastasis directed therapies aimed at personalizing the treatment for every single patient.

Low PSA radiographic disease progression on C11-choline PET

Background

For men with prostate cancer, radiographic progression may occur without a concordant rise in prostate-specific antigen (PSA). Our study aimed to assess the prevalence of radiographic progression using C-11 choline positron emission tomography (PET) imaging in patients achieving ultra-low PSA values and to evaluate clinical outcomes in this patient population.

Methods

In a single institution study, we reviewed the prospectively maintained Mayo Clinic C-11 Choline PET metastatic prostate cancer registry to identify patients experiencing radiographic disease progression (rDP) on C-11 choline PET scan while the PSA value was less than 0.5 ng/mL. Disease progression was confirmed by tissue biopsy or response to subsequent therapy. Clinicopathologic variables were abstracted by trained research personnel. Overall survival was estimated using the Kaplan-Meier method. Intergroup differences were assessed using the log-rank test. A univariate and multivariate Cox regression model was performed to investigate variables associated with poor survival after rDP.

Results

A total of 1323 patients within the registry experienced rDP between 2011 and 2021, including 220 (16.6%) men with rDP occurring at low PSA level. A median (interquartile range [IQR]) of 54.7 (19.7-106.9) months elapsed between the time of prostate cancer diagnosis and low PSA rDP, during which 173 patients (78%) developed castration-resistant prostate cancer (CRPC). Sites of low PSA rDP included local recurrence (n = 17, 8%), lymph node (n = 90, 41%), bone (n = 94, 43%) and visceral metastases (n = 19, 9%). Biopsy at the time of rDP demonstrated small-cell or neuroendocrine features in 21% of patients with available tissue. Over a median (IQR) follow-up of 49.4 (21.3-95.1) months from the time of low PSA rDP, 46% (n = 102) of patients died. Factors associated with poorer survival outcomes include advanced age at rDP, CRPC status, bone and visceral metastasis (p value <0.05). Visceral metastases were associated with decreased overall survival (p = 0.009 by log-rank) as compared with other sites of rDP.

Conclusions

Men with prostate cancer commonly experience metastatic progression at very low or even undetectable PSA levels. Periodic imaging, even at low absolute PSA values, may result in more timely identification of disease progression.

Nuclear medicine imaging for bone metastases assessment: what else besides bone scintigraphy in the era of personalized medicine?

Accurate detection and reliable assessment of therapeutic responses in bone metastases are imperative for guiding treatment decisions, preserving quality of life, and ultimately enhancing overall survival. Nuclear imaging has historically played a pivotal role in this realm, offering a diverse range of radiotracers and imaging modalities. While the conventional bone scan using 99mTc marked bisphosphonates has remained widely utilized, its diagnostic performance is hindered by certain limitations. Positron emission tomography, particularly when coupled with computed tomography, provides improved spatial resolution and diagnostic performance with various pathology-specific radiotracers. This review aims to evaluate the performance of different nuclear imaging modalities in clinical practice for detecting and monitoring the therapeutic responses in bone metastases of diverse origins, addressing their limitations and implications for image interpretation.

Current status of PSMA-targeted imaging and therapy

Currently, the incidence of prostate cancer is increasing, and it has become a great threat to men's health. The detection, staging, and follow-up of prostate cancer patients are inseparable from morphology or magnetic resonance imaging (MRI). However, these do not fully meet the needs of diagnosis and patient management. In particular, owing to the late diagnosis, metastatic castration-resistant prostate cancer (mCRPC) patients usually have poor survival and few options for further effective treatment. Prostate-specific membrane antigen (PSMA), because of its overexpression on prostate cancer cells, has gained interest due to its application in the imaging and theranostics field. Several PSMA radioligands have been developed for imaging and treating prostate cancer. Many clinical trials have assessed the efficacy and safety profiles of these radionuclide agents and show promise in patients who have exhausted other standard treatment options. To date, several small compounds for targeting PSMA have been developed, and 68Ga-PSMA-11 and 18F-DCFPyL have been approved by the United States (US) Food and Drug Administration (FDA) for imaging of prostate cancer. 111In- or 99mTc-labeled PSMA-ligand can guide surgeons searching for radioactive metastatic lymph nodes, and 177Lu- or 225Ac-labeled PSMA-ligand can be used for internal radiotherapy. Moreover, some molecules for therapeutic application are undergoing different stages of clinical trials. In this review, we present current perspectives on the use of PSMA-targeted imaging and theranostics in prostate cancer. As PSMA-targeted imaging and therapeutics are becoming the standard of care for prostate cancer patients, we emphasize the importance of integrating nuclear medicine physicians into multidisciplinary oncology teams.

Comparison of Hormone-Sensitive Oligorecurrent Prostate Cancer Patients Based on Routine Use of Choline and/or PSMA PET/CT to Guide Metastasis-Directed Therapy

BACKGROUND

In hormone-sensitive oligorecurrent prostate cancer (PC), the literature showed [68Ga]Ga-PSMA (PSMA) and [18F]F-choline (FCH) PET/CT can successfully guide metastasis-directed therapies (MDT). This observational retrospective study aimed to explore, in routine use, the impact of FCH or PSMA PET/CT in guiding MDT for hormone-sensitive oligometastatic PC at different recurrences.

METHODS

In 2017-2020, patients initially treated with radical prostatectomy but, in biochemical recurrence (with PSA ≤ 2 ng/mL), diagnosed as oligometastatic based on FCH or PSMA PET/CT, were identified. MDT was stereotactic body radiotherapy (SBRT), elective nodal or prostate bed radiotherapy ± boost and ± androgen deprivation therapy (ADT). The primary endpoint was biochemical relapse-free survival (BR-FS), defined as a PSA increase ≥ 0.2 ng/mL above the nadir and increasing over two successive samples and the secondaries were ADT-free survival (ADT-FS).

RESULTS

123 patients (70 PSMA and 53 FCH) were included. The median follow-up was 42.2 months. The median BR-FS was 24.7 months in the PSMA group versus 13.0 months in the FCH group (p = 0.008). Similarly, ADT-FS (p = 0.001) was longer in patients in the PSMA group. In multivariate analysis, a short PSA doubling time before imaging (p = 0.005) and MDT with SBRT (p = 0.001) were poor prognostic factors for BR-FS.

CONCLUSIONS

Routine use of FCH or PSMA PET/CT in hormone-sensitive PC showed an advantage for using PSMA PET/CT to guide MDT in terms of BR-FS and ADT-FS in patients with low PSA value. Prospective studies are needed to confirm these hypotheses.

68Ga-PSMA PET/CT in early relapsed prostate cancer patients after radical therapy

Biochemical recurrence (BCR) of prostate cancer (PCa) occurs in about 25% of patients treated with radical prostatectomy (RP) and up to 45% in patients who receive external beam radiotherapy (RT). Early diagnosis of PCa recurrence is of high importance for successful salvage therapy. The aim of the present study is to analyze the efficacy of ⁶⁸ Ga-PSMA PET/CT in detecting the presence of local and/or systemic disease in patients with a history of PCa who have BCR. A total of 52 PCa patients with BCR referred for ⁶⁸ Ga-PSMA PET/CT were recruited from the American University of Beirut Medical Center between November 2017 and December 2019. We compared the performance of PSMA PET/CT to the results and clinical factors based on follow up: PSA, PSA kinetics, primary treatment, and Gleason score. The relationship between the PET/CT findings and clinical indicators of disease were assessed by univariate and multivariate logistic regression. From a total of 52 patients, 34 (65.4%) had positive PSMA-PET/CT scans. Among those, 8/34 (23.5%) received primary RT. For all patients with a positive PSMA-PET: the detection rate was 2/4 (50%) for PSA < 0.2, 5/10 (50%) for PSA 0.2-0.49, 3/6 (50%) for PSA 0.5-0.99, 6/12 (50%) for PSA 1-1.99, 8/9 (88.9%) for PSA 2-3.99, and 10/11 (90.9%) for PSA 4-10.PSMA-PET/CT positivity was significantly associated with PSA level at time of PET scan, PSA doubling time, Gleason score and TNM staging. However, it did not show a significant correlation with radiotherapy as primary treatment, ongoing androgen deprivation therapy (ADT), time to relapse, and initial PSA before therapy. In our single center prospective trial, ⁶⁸ Ga-PSMA PET/CT successfully detected the recurrence of PCa in patients with BCR. Scan positivity was significantly associated with PSA level at time of PET scan, PSA doubling time, Gleason score, and TNM staging. PSMA- PET/CT is a highly promising modality in the work up of patients with PCa in the setting of BCR for earlier detection of disease recurrence.

[18F]fluciclovine vs. [18F]fluorocholine Positron Emission Tomography/Computed Tomography: A Head-to-Head Comparison for Early Detection of Biochemical Recurrence in Prostate Cancer Patients

Nowadays, there is still no consensus on the most accurate PET radiopharmaceutical to early detect prostate cancer (PCa) relapse. A tailored radiotracer choice based on a specific patient's profile could ensure prompt disease detection and an improvement in patients management. We aimed to compare the [18F]fluciclovine and [18F]fluorocholine PET/CT detection rate (DR) in PCa patients restaged for early biochemical recurrence (BCR), according to clinical and biochemical features. A cohort of 138 PCa patients with early BCR (mean age: 71 y, range: 50-87 y) were homogeneously randomized 1:1 to a [18F]fluciclovine or a [18F]fluorocholine PET/CT group. The respective PET/CT DR, according to per-patient and per-region analysis, and the impact of the biochemical, clinical, and histological parameters, were compared. The PSA cut-off values predictive of a positive scan were also calculated. Overall, the [18F]fluciclovine PET/CT DR was 64%, significantly higher than the [18F]fluorocholine PET/CT DR of 35% (p = 0.001). Similarly, in the per-region analysis, the [18F]fluciclovine PET/CT DR was 51% in the prostate region, significantly higher compared to 15% of [18F]fluorocholine (p < 0.0001). Furthermore, a statistically significant higher DR in per-patient and per-region (prostate/prostate bed) analysis was observed in the [18F]fluciclovine group for 0.5-1 ng/mL (p = 0.018, p = 0.049) and >1 ng/mL (p = 0.040, p < 0.0001) PSA values. A PSA of 0.45 ng/mL for [18F]fluciclovine and of 0.94 ng/mL for [18F]fluorocholine was identified as the optimal cut-off value in predicting a positive PET/CT scan. Our results demonstrated a better [18F]fluciclovine PET/CT DR compared to [18F]fluorocholine for restaging PCa patients in early BCR, particularly in the detection of locoregional recurrence. The significantly higher [18F]fluciclovine DR for low PSA values (PSA < 1 ng/mL) supports its use in this setting of patients.

Assessment of volumetric parameters derived from 68Ga-PSMA PET/CT in prostate cancer patients with biochemical recurrence: an institutional experience

OBJECTIVE

The aim of this study was to evaluate the relationship between volumetric parameters calculated using semiautomatic quantification of lesions detected in 68Ga-labeled prostate-specific membrane antigen PET-computed tomography (68Ga-PSMA PET/CT) and clinical characteristics in prostate cancer (PCa) patients with biochemical recurrence.

METHODS

A total of 85 consecutive PCa patients with biochemical recurrence who underwent 68Ga-PSMA PET/CT at our institution from January 2019 to March 2020 were retrospectively assessed. 68Ga-PSMA PET/CT-derived volumetric parameters, including whole-body PSMA tumor volume (wbPSMA-TV) and whole-body total lesion PSMA (wbTL-PSMA), as well as the established maximum and mean standardized uptake value (SUVmax and SUVmean), were calculated for each patient. All PET-derived parameters were analyzed for correlation with prostate-specific antigen (PSA) levels and for association with Gleason scores.

RESULTS

Eighty-five patients with a mean age of 68.9 ± 7.8 years (range, 47-83 years) and a mean PSA level of 40.9 ± 92.1 ng/ml (range, 0.2-533.2 ng/ml) were analyzed. Volumetric parameters, that is, wbPSMA-TV and wbTL-PSMA, demonstrated a statistically significant correlation with PSA levels (r = 0.403 and r = 0.556, respectively, all at P < 0.001) and only the means of wbTL-PSMA were significantly different between the Gleason score groups (P < 0.05).

CONCLUSIONS

The results of our study indicate that 68Ga-PSMA PET/CT might be a valuable tool for the detection and follow-up of recurrence in PCa patients. 68Ga-PSMA PET/CT-derived quantitative volumetric parameters demonstrated a highly significant correlation with changes in PSA levels. Larger prospective studies are needed to help reveal the full potential of parameters such as PSMA-TV and TL-PSMA derived from PET imaging with 68Ga-PSMA.

Prostate cancer: Molecular imaging and MRI

The role of molecular imaging in initial evaluation of men with presumed or established diagnosis of prostate cancer and work up of biochemical recurrence and metastatic disease is rapidly evolving due to superior diagnostic performance compared to anatomic imaging. However, variable tumor biology and expression of transmembrane proteins or metabolic alterations poses a challenge. We review the evidence and controversies with emphasis on emerging PET radiopharmaceuticals and experience on clinical utility of PET/CT and PET/MRI in diagnosis and management of prostate cancer.

Negative 11C-choline PET/computed tomography imaging in restaging of patients with prostate cancer with serum prostate-specific antigen values >20 ng/mL

OBJECTIVE

Several studies have reported about the performance of C-choline-PET/computed tomography (CT) (choline) in patients with biochemical recurrent (BCR) prostate cancer, but there is a lack of information regarding negative choline in the same clinical setting. Our aim was to retrospectively analyse negative choline in a cohort of BCR-patients with high prostate-specific antigen (PSA).

METHODS AND RESULTS

We retrospectively analysed all choline-scans performed at two high-volume imaging centres between 2005 and 2018, selecting those of interest according to the following inclusion criteria: (1) proven prostate cancer treated either with radical prostatectomy or primary external beam radiation therapy (EBRT), (2) BCR after radical prostatectomy or EBRT, (3) PSA serum values >20 ng/mL at the time of scan and (4) scan reported as negative for active disease. Overall, among 5792 scans performed for BCR-prostate cancer, 14 matched the inclusion criteria and were classified as follows: 5/14(36%) inaccurate reports, 3/14(21%) questionable underestimation of positive findings, originally described as unclear, 6/14(43%) negatives. Choline showed a high detection rate in BCR-prostate cancer patients with PSA >20 ng/mL.

CONCLUSIONS

Although negative reports can be found in this clinical setting, in our review various disease-relevant findings were identified in more than half of the cases originally reported as negative warranting a double reading in such cases to avoid false-negative reports.

EAU-EANM-ESTRO-ESUR-SIOG Guidelines on Prostate Cancer. Part II-2020 Update: Treatment of Relapsing and Metastatic Prostate Cancer

OBJECTIVE

To present a summary of the 2020 version of the European Association of Urology (EAU)-European Association of Nuclear Medicine (EANM)-European Society for Radiotherapy & Oncology (ESTRO)-European Society of Urogenital Radiology (ESUR)-International Society of Geriatric Oncology (SIOG) guidelines on the treatment of relapsing, metastatic, and castration-resistant prostate cancer (CRPC).

EVIDENCE ACQUISITION

The working panel performed a literature review of the new data (2016-2019). The guidelines were updated, and the levels of evidence and/or grades of recommendation were added based on a systematic review of the literature.

EVIDENCE SYNTHESIS

Prostate-specific membrane antigen positron emission tomography computed tomography scanning has developed an increasingly important role in men with biochemical recurrence after local therapy. Early salvage radiotherapy after radical prostatectomy appears as effective as adjuvant radiotherapy and, in a subset of patients, should be combined with androgen deprivation. New treatments have become available for men with metastatic hormone-sensitive prostate cancer (PCa), nonmetastatic CRPC, and metastatic CRPC, along with a role for local radiotherapy in men with low-volume metastatic hormone-sensitive PCa. Also included is information on quality of life outcomes in men with PCa.

CONCLUSIONS

The knowledge in the field of advanced and metastatic PCa and CRPC is changing rapidly. The 2020 EAU-EANM-ESTRO-ESUR-SIOG guidelines on PCa summarise the most recent findings and advice for use in clinical practice. These PCa guidelines are first endorsed by the EANM and reflect the multidisciplinary nature of PCa management. A full version is available from the EAU office or online (http://uroweb.org/guideline/prostate-cancer/).

PATIENT SUMMARY

This article summarises the guidelines for the treatment of relapsing, metastatic, and castration-resistant prostate cancer. These guidelines are evidence based and guide the clinician in the discussion with the patient on the treatment decisions to be taken. These guidelines are updated every year; this summary spans the 2017-2020 period of new evidence.

Development of a technique for evaluating the presence of malignant cells in prostatic fluid during robotic prostatectomy

INTRODUCTION

To develop a technique to collect fluid expressed during robot-assisted radical prostatectomy (RARP) to assess whether malignant cells may have been inadvertently introduced into the surgical field.

METHODS

Men with clinically localized grade group 2 to 5 prostate adenocarcinoma undergoing RARP were identified. Following bladder neck division, fluid expressed via prostatic urethra during seminal vesicle dissection was aspirated (specimen A). After specimen removal, an ex vivo seminal vesicle aspiration was performed as well (specimen B). Specimens were prepared with ThinPrep (Hologic, Marlborough, MA) and stained with 4 immunohistochemical markers: keratin-7, PAX-8, prostate-specific antigen (PSA), and prostatic acid phosphatase (PACP).

RESULTS

Between December 2018 and May 2019, 15 men undergoing RARP were included. Median age was 60 years (range: 47-77), median PSA 8.5 ng/ml (range 5.1-24), and 7 (47%) had AUA high-risk disease. Specimen A had adequate cellularity in 13 patients (87%). Five patients were excluded from assessment of malignancy due to acellularity of specimen A (n = 2) or specimen B (n = 3). Three of the remaining 10 patients (30%) had cytologic features suspicious for malignancy on specimen A. Immunohistochemistry supported prostatic origin with positive PSA and PACP staining and negative PAX8 stains. Specimen B was not suspicious in any patient.

CONCLUSION

We report a technique for intraoperative collection of fluid expressed during RARP. Three patients with adverse pathologic features had evidence of cancer cells within the operative field. Further work is needed to confirm this observation and to determine whether these cells are associated with adverse oncologic outcomes.

Molecular imaging of prostate cancer: Review of imaging agents, modalities, and current status

INTRODUCTION

The clinical course of Prostate cancer (PCa) are markedly diverse, ranging from indolent to highly aggressive disseminated disease. Molecular imaging techniques are playing an increasing role in early PCa detection, staging and disease recurrence. There are some molecular imaging modalities, radiotracers agents and its performance are important in current clinical practice PCa.

OBJECTIVE

This review summarizes the latest information regarding molecular imaging of PCa and is designed to assist urologists with ordering and interpreting these modalities and different radiotracers for different patients.

EVIDENCE ACQUISITION

A PubMed-based literature search was conducted up to September 2019. We selected the most recent and relevant original articles, metanalysis and reviews that have provided relevant information to guide molecular imaging modalities and radiotracers use.

EVIDENCE SYNTHESIS

In this review, we discuss 3 main molecular imaging modalities and 7 radiotracer technologies available.

CONCLUSIONS

The use molecular imaging modalities and radiotracers has a unique role in biochemical recurrence and diagnosis of ganglionar and bone progression of PCa. In the present time, no one of these molecular imaging modalities can be recommended over the classical work-up of abdominopelvic CT scan and bone scan, and large-scale and multi-institutional studies are required to validate the efficacy and cost utility of these new technologies.

Prostate-Specific Membrane Antigen-Targeted Radiopharmaceuticals in Diagnosis and Therapy of Prostate Cancer: Current Status and Future Perspectives

Prostate cancer is the most common cancer to affect men in the United States and the second most common cancer in men worldwide. Prostate-specific membrane antigen (PSMA)-based positron emission tomography (PET) imaging has become increasingly popular as a novel molecular imaging technique capable of improving the clinical management of patients with prostate cancer. To date, several ⁶⁸Ga and ¹⁸F-labeled PSMA-targeted molecules have shown promising results in imaging patients with recurrent prostate cancer using PET/computed tomography (PET/CT). Studies of involving PSMA-targeted radiopharmaceuticals also suggest a higher sensitivity and specificity, along with an improved detection rate over conventional imaging (CT scan and methylene diphosphonate bone scintigraphy) and ¹¹C/¹⁸F-choline PET/CT. In addition, PSMA-617 and PSMA I&T ligands can be labeled with α- and β-emitters (e.g., ²²⁵Ac, ⁹⁰Y, and ¹⁷⁷Lu) and serve as a theranostic tool for patients with metastatic prostate cancer. While the clinical impact of such concept remains to be verified, the preliminary results of PSMA molecular radiotherapy are very encouraging. Herein, we highlighted the current status of development and future perspectives of PSMA-targeted radiopharmaceuticals and their clinical applications.

Multiphasic 68Ga-PSMA PET/CT in the Detection of Early Recurrence in Prostate Cancer Patients with a PSA Level of Less Than 1 ng/mL: A Prospective Study of 135 Patients

The main objective of this prospective study was to determine the impact of multiphasic acquisition of ⁶⁸Ga-PSMA PET/CT in the detection of recurrent prostate cancer in the early stage of biochemical recurrence with a prostate-specific antigen (PSA) level of less than 1 ng/mL. Also, ⁶⁸Ga-PSMA PET/CT positivity was correlated with clinical parameters for the assessment of predictive markers. Methods: A prospective monocentric study was conducted on 135 prostate cancer patients with biochemical recurrence and a PSA level of less than 1 ng/mL. All patients had undergone initial prostatectomy, with additional radiation therapy in 19.3% of patients and androgen-deprivation therapy in 7.4%. The patients underwent dynamic acquisitions from the prostate bed (1-8 min after injection), standard whole-body acquisitions (60 min after injection), and limited-bed-position delayed acquisitions (120-150 min after injection). The studies were reviewed by 2 board-certified nuclear medicine specialists, independently. A combination of visual and semiquantitative analyses and correlation with morphologic (e.g., MRI) or clinical follow-up findings was used for the final interpretation of lesions as benign or malignant. ⁶⁸Ga-prostate-specific membrane antigen (PSMA) PET/CT positivity was also correlated with primary clinical findings. Results: Incorporating the information from all phases, we were able to detect 116 lesions in 49.6% of patients (22 local recurrences, 63 lymph nodes, and 31 distant metastases). The detection rates were 31.8%, 44.9%, and 71.4% for PSA < 0.2 ng/mL, 0.2 ≤ PSA < 0.5, and 0.5 ≤ PSA < 1, respectively. Additional dynamic or delayed phases resulted in better determination of equivocal lesions and a higher diagnostic performance in 25.9% of patients. Stand-alone dynamic and delayed images led to better interpretation of equivocal findings in the prostate bed (31.4%) and in other lesions (lymph node or bone) (20%), respectively. Conclusion: ⁶⁸Ga-PSMA PET/CT showed promise for early detection of recurrent disease in patients with a PSA level of 0.5-1.0 ng/mL. However, it showed limited value in patients with a PSA level of less than 0.5 ng/mL. Multiphasic ⁶⁸Ga-PSMA PET/CT led to a better determination of equivocal findings. Although dynamic images may provide helpful information for assessment of the prostate bed, delayed acquisitions seem to have a greater impact in clarifying equivocal findings.

Imaging for Metastasis in Prostate Cancer: A Review of the Literature

Background: Initial staging and assessment of treatment activity in metastatic prostate cancer (PCa) patients is controversial. Indications for the various available imaging modalities are not well-established due to rapid advancements in imaging and treatment.

Methods: We conducted a critical literature review of the main imaging abnormalities that suggest a diagnosis of metastasis in localized and locally advanced PCa or in cases of biological relapse. We also assessed the role of the various imaging modalities available in routine clinical practice for the detection of metastases and response to treatment in metastatic PCa patients.

Results: In published clinical trials, the most commonly used imaging modalities for the detection and evaluation of therapeutic response are bone scan, abdominopelvic computed tomography (CT), and pelvic and bone magnetic resonance imaging (MRI). For the detection and follow-up of metastases during treatment, modern imaging techniques i.e., choline-positron emission tomography (PET), fluciclovine-PET, or Prostate-specific membrane antigen (PSMA)-PET provide better sensitivity and specificity. This is particularly the case of fluciclovine-PET and PSMA-PET in cases of biochemical recurrence with low values of prostate specific antigen.

Conclusions: In routine clinical practice, conventional imaging still have a role, and communication between imagers and clinicians should be encouraged. Present and future clinical trials should use modern imaging methods to clarify their usage.

Lung uptake of fluorine-18 fluoroethyl-choline PET-CT in patients with prostate cancer

BACKGROUND

Metastatic spreading to the lungs is a negative prognostic factor in patients with prostate cancer (PC). Aim of our study was to assess the prevalence of lung PC metastases in patients with fluorine-18 fluoroethyl-choline (F-18-FECh) PET-CT positive lung lesions and the role of Gleason Score (GS) and common biochemical markers in predicting metastatic spreading to the lungs.

METHODS

We retrospectively evaluated the scans of 1283 patients ongoing (F-18-FECh) PET-CT for PC between May 2010 and July 2014. Patients with lung lesion with F-18-FECh uptake were included. Data concerning GS at diagnosis, "trigger" prostate-specific antigen (PSAtr), PSA doubling time (PSAdt), PSA velocity (PSAvel) and ongoing androgen deprivation therapy were collected. PET-CT findings were confirmed by histology or follow-up (FU) and classified as follows: inflammation, primary lung cancer or metastases from tumor other than PC, and lung metastases from PC.

RESULTS

Twenty-two patients with F-18-FECh positive lung lesion and available histology or FU were identified. PSAdt was significantly (P=0.029) shorter in patients with lung metastases from PC (median PSAdt 1.7 months, interquartile range [IQR] 1.5-4.1 months) than in patients without lung PC relapse (median PSAdt 6.7 months, IQR 3.9-7.8); PSAvel was significantly (P=0.019) higher in patients with lung metastases from PC (median PSAvel 3.2 ng/mL/month, IQR 0.65-6.65 ng/mL/month) than in patients without lung PC relapse (median PSAvel 0.3 ng/mL/month, IQR 0.2-0.5 ng/mL/month). Patients with lung metastases from PC had significantly (P=0.006) higher GS at diagnosis (median GS 8) than the other ones (median GS 7).

CONCLUSIONS

Our analysis shows that the prevalence of F-18-FECh positive lung metastases in patients with PC, especially with higher GS at diagnosis, is higher in presence of a steady increase in PSA values, confirmed by higher PSAvel and shorter PSAdt.

Prostate-Specific Membrane Antigen PET/Magnetic Resonance Imaging for the Planning of Salvage Radiotherapy in Patients with Prostate Cancer with Biochemical Recurrence After Radical Prostatectomy

This article presents an overview of the current literature on PET imaging with prostate-specific membrane antigen ligands, especially focusing on the potential role of simultaneous PET/magnetic resonance imaging for the planning of salvage radiotherapy in patients with prostate cancer with biochemical recurrence after radical prostatectomy.

Recurrent prostate cancer after radical prostatectomy: restaging performance of 18F-choline hybrid PET/MRI

To evaluate the diagnostic performance of a whole-body 18F-choline (FCH) hybrid PET/MRI for prostate cancer patients at biochemical relapse after radical prostatectomy (RP) compared to pelvic multiparametric MRI (mpMRI), one of the standard imaging modality for this patient population. From 2010 to 2016, 58 whole-body FCH PET/MRI studies with mpMRI acquisitions were performed in 53 prostate cancer patients relapsing after curative RP. Median PSA and PSA doubling time (PSA DT) at PET study were 1.5 ng/ml and 6.5 months, respectively. The overall positivity rate of FCH PET/MRI was 58.6% (n = 34), dropping to 44% in patients with a PSA ≤ 2 ng/ml (n = 36). Median PSA values in positive and negative PET/MRI studies were 2.2 ng/ml and 0.8 ng/ml, respectively, with no differences in PSA DT (6.5 vs. 6.6 months). A PSA value ≥ 1.5 ng/ml was a significant predictor of positivity on PET/MRI studies. Compared to PET, mpMRI identified more local relapses (17 vs. 14, p = 0.453) while PET outperformed whole-body Dixon MRI for regional (16 vs. 9, p = 0.016) and distant (12 vs. 6, p = 0.031) metastases. Compared to pelvic mpMRI, the treatment approach turned out to be influenced more frequently using whole-body FCH hybrid PET/MRI studies (58.6% vs. 38%). In prostate cancer patients with biochemical recurrence after RP, whole-body FCH PET/MRI achieved a higher detection rate of nodal/distant metastases compared to pelvic mpMRI alone, increasing the change of treatment strategy by more than 20%.

68Ga-PSMA PET/CT in Patients with Rising Prostatic-Specific Antigen After Definitive Treatment of Prostate Cancer: Detection Efficacy and Diagnostic accuracy

RATIONALE AND OBJECTIVES

68Ga-prostate-specific membrane antigen-11 (68Ga-PSMA-11) is a recently developed positron emission tomography (PET) tracer that can detect prostate cancer (PC) relapses and metastases with high contrast resolution. The aim of this study was to assess the detection efficacy and diagnostic accuracy of 68Ga-PSMA PET/CT image in patients with rising prostatic-specific antigen (PSA) after treatment of PC.

MATERIALS AND METHODS

The present prospective study included 188 patients who exhibited rising of PSA level on a routine follow-up examination after definitive treatment of PC. All patients underwent a 68Ga-PSMA PET/CT examination. For each patient, we determined the disease stage, the Gleason score, and the maximum standardized uptake value of the local recurrence and extraprostatic metastases. The detection efficacy and diagnostic accuracy of 68Ga-PSMA PET/CT were established by histopathology and clinical and imaging follow-up as the reference standards.

RESULTS

68Ga-PSMA PET/CT detected tumour relapse in 165 patients (35 patients had local recurrence, 106 patients had extraprostatic metastases, and 24 patients had combined lesions). The sensitivity, specificity, and accuracy values of 68Ga-PSMA PET/CT examination in the detection of PC recurrence were 98.8%, 100%, and 98.8%, respectively. 68Ga-PSMA PET/CT revealed an overall detection rate of 87.8% (165/188) in patients with rising PSA (median of 2.2 ng/mL, and range of 0.01-70 ng/mL).

CONCLUSION

68Ga-PSMA PET/CT is a valuable tool for the detection of PC local recurrence or extraprostatic metastases following rising PSA levels after primary definitive therapy and should be incorporated during routine work-up.

Initial experience of Ga-68 prostate-specific membrane antigen positron emission tomography/computed tomography imaging in evaluation of biochemical recurrence in prostate cancer patients

Gallium-68 labeled prostate-specific membrane antigen (Ga-68 PSMA) ligand (HBED-CC) is a novel tracer used for prostate cancer imaging. The aim of the study was to investigate the performance of Ga-68 PSMA positron emission tomography/computed tomography (PET/CT) in patients with biochemical recurrence (BCR) after definitive treatment. Scans of 96 consecutive patients were analyzed. Sixty-two patients received external beam radiotherapy, 34 underwent radical prostatectomy (RP), and 20 patients were on androgen deprivation therapy. Patients with prostate-specific antigen (PSA) level ≥>0.2 ng/mL following RP and PSA rise by 2 ng/mL or more above the nadir PSA following RT (Phoenix criteria) was considered as BCR, respectively. All patients underwent contrast-enhanced PET/CT after injection of 67–111 MBq Ga-68 PSMA ligand. Detection rates were correlated with serum PSA level. Detection rate for nodal metastases was compared with CT. Results of the scan were validated by using either biopsy or follow-up imaging or clinical follow-up. Seventy-four (77%) patients showed abnormal finding in Ga-68 PSMA PET/CT. The median serum PSA level of the population was 5.5 ng/ml (range 0.2–123 ng/ml). The median PSA of the positive scans was higher than that of the negative scans (6 vs. 1.7 ng/ml) and was statistically significant (P = 0.001 by Mann–Whitney U-test). In post-RP group, the detection rates were 23%, 50%, and 82% for PSA <1, 1–2, and >2 ng/ml, respectively. For post-RT, the detection was 86%, 85%, and 95% for PSA 2–5, 5.1–10, and >10 ng/ml, respectively. PSMA PET/CT revealed nodal metastases in 52 (54%) patients while CT showed pathological nodes only in 27 (28%) patients. Overall PSMA PET/CT revealed more number of nodes than CT (111 vs. 48 nodal station). PSMA PET/CT showed relapse in prostate/prostatic bed in 26 (27%) patients, nodal metastases in 50 (52%), skeletal metastases in 20 (21%), and other sites in 4 (4%) patients. Ga-68 PSMA PET/CT has high detection rate for localizing the site of recurrence in patients with biochemical failure and is superior to CT scan in the detection of nodal disease.

Detection rates of recurrent prostate cancer: 68Gallium (Ga)-labelled prostate-specific membrane antigen versus choline PET/CT scans. A systematic review

BACKGROUND

The aim of this work was to assess the use of prostate-specific membrane antigen (PSMA)-labelled radiotracers in detecting the recurrence of prostate cancer. PSMA is thought to have higher detection rates when utilized in positron emission tomography (PET)/computed tomography (CT) scans, particularly at lower prostate-specific antigen (PSA) levels, compared with choline-based scans.

METHODS

A systematic review was conducted comparing choline and PSMA PET/CT scans in patients with recurrent prostate cancer following an initial curative attempt. The primary outcomes were overall detection rates, detection rates at low PSA thresholds, difference in detection rates and exclusive detection rates on a per-person analysis. Secondary outcome measures were total number of lesions, exclusive detection by each scan on a per-lesion basis and adverse side effects.

RESULTS

Overall detection rates were 79.8% for PSMA and 66.7% for choline. There was a statistically significant difference in detection rates favouring PSMA [OR (M-H, random, 95% confidence interval (CI)) 2.27 (1.06, 4.85), p = 0.04]. Direct comparison was limited to PSA < 2 ng/ml in two studies, with no statistically significant difference in detection rates between the scans [OR (M-H, random, 95% CI) 2.37 (0.61, 9.17) p = 0.21]. The difference in detection on the per-patient analysis was significantly higher in the PSMA scans (p < 0.00001). All three studies reported higher lymph node, bone metastasis and locoregional recurrence rates in PSMA.

CONCLUSIONS

PSMA PET/CT has a better performance compared with choline PET/CT in detecting recurrent disease both on per-patient and per-lesion analysis and should be the imaging modality of choice while deciding on salvage and nonsystematic metastasis-directed therapy strategies.

Clinical implications of PET/CT in prostate cancer management

Several imaging modalities exist for the investigation of prostate cancer (PCa). From ultrasound to computed tomography (CT) and magnetic resonance imaging (MRI), the role of imaging in detecting lesion foci, staging, and localizing disease after biochemical recurrence (BCR) is expanding. However, many of the conventional imaging modalities are suboptimal, particularly in the detection of metastasis. Positron emission tomography (PET) has recently emerged as a promising tool in PCa management. The ability to develop radiolabeled tracers for functional imaging based on characteristics of PCa cells can potentially provide more insight into management by utilizing key features of those cells, such as metabolic activity, increased proliferation, and receptor expression. 18-flurodeoxyglucose (FDG) is one of the earliest tracers used in PET imaging that takes advantage of increased metabolism of glucose. Its role in PCa has been somewhat limited due to poor resolution and confounders including noise resulting from the proximity of the prostate to the bladder. Choline, a precursor molecule for a major component of the cell membrane, phosphatidylcholine, shows increased uptake in cells with rapid proliferation. When compared to metabolic based imaging techniques with FDG, choline PET/CT was superior. Nevertheless, choline PET/CT was not equivocal to MRI in detection of local disease, but was superior to conventional imaging in localizing metastasis and lymph node metastasis (LNM). Fluciclovine is another novel marker that utilizes the increased proliferation seen in tumor cells. Studies have shown it to be superior to choline PET/CT in PCa management, particularly in patients with BCR. As with choline PET/CT, studies that have assessed the impact of fluciclovine on clinical practice have highlighted the impact of these new tracers on clinical decision making. Most recently, the newest molecular probe targeting prostate specific membrane antigen (PSMA) was developed. It offers higher detection rates compared to choline PET/CT and conventional imaging modalities and has shown promise in LNM and BCR. With the wide range of available PET tracers, this review aims to highlight the role of each in lesion foci detection, primary staging, disease recurrence and explore the potential clinical impact.

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.

Imaging of Prostate Cancer Using 11C-Choline PET/Computed Tomography

This article reviews the role of ¹¹C-choline-PET/computed tomography (CT) in patients with prostate cancer for diagnosis, staging, and restaging the disease in case of biochemical recurrence after primary treatment. The main application of this imaging procedure is restaging of the disease in case of biochemical recurrence. ¹¹C-Choline-PET/CT proved its value for metastases-directed salvage therapies and for monitoring therapy response in castration-resistant patients. Prostate-specific antigen and prostate-specific antigen kinetics values confirmed their correlation with ¹¹C-choline PET/CT sensitivity.¹¹C-CholinePET/CT, despite low sensitivity to stage disease or in case of biochemical failure with low PSA levels, has an important impact on the management of patients with prostate cancer.

The utility of PET-based imaging for prostate cancer biochemical recurrence: a systematic review and meta-analysis

INTRODUCTION

Conventional imaging modalities have been poor in characterizing the true extent of disease in men with biochemical recurrence following primary treatment for prostate cancer. Functional imaging with positron emission tomography (PET) has shown promise of being a superior imaging modality. We conducted a systematic review and meta-analysis to define the diagnostic accuracy of PET/CT using 11C-choline, 18F-FACBC, or 68Ga-PSMA in detecting recurrent prostate cancer.

METHODS

We searched multiple databases in line with the preferred reporting items for systematic review and meta-analysis (PRISMA) statement to define the diagnostic accuracy of 11C-choline, 18F-FACBC, or 68Ga-PSMA PET/CT. Only studies secondarily staging participants with biochemical recurrence and those with an appropriate reference standard (pathology, further imaging, and/or clinical response) were eligible for analysis.

RESULTS

Twenty-one studies with 3202 participants met the inclusion criteria. Of these, 11C-choline, 18F-FACBC, and 68Ga-PSMA were the tracer investigated in 16, 5, and 1 studies, respectively. The summary sensitivity for each tracer was 80.9% (95% CI 70.4-88.3%), 79.7% (95% CI 51.9-93.4%), and 76.4% (95% CI 68.3-82.9%), respectively. The corresponding summary specificity was 84.1% (95% CI 70.2-92.2%), 61.9% (95% CI 41.1-79.0%), and 99.8% (95% CI 97.5-100%), respectively. Detection rates ranged between 58.6 and 82.8%. All included studies were judged to be at high risk of bias primarily due to study limitations pertaining to the reference standard.

CONCLUSION

There is a lack of high-quality data to verify the accuracy of PET-based imaging using 11C-choline, 18F-FACBC, or 68Ga-PSMA. The early results are encouraging that these techniques are superior to conventional imaging modalities, which would allow salvage therapies to be optimized.

Predictor of 68Ga PSMA PET/CT positivity in patients with prostate cancer

BACKGROUND

The aim of this study was to evaluate predictive factors of 68Gallium (68Ga) prostate-specific membrane antigen (PSMA) positron emission tomography (PET)/computed tomography (CT) positivity.

METHODS

Relationships between serum prostate specific antigen (PSA), lactate dehydrogenase (LDH) and alkaline phosphatase (ALP) levels, Gleason Score (GS) and positivity of 68Ga PSMA PET in patients who underwent 68Ga PSMA PET/CT for restaging for PCa were evaluated retrospectively.

RESULTS

One hundred and four (median age: 67; range: 51-88) patients were included in this study. Of these patients, PSMA PET was positive in 75 (72%) patients. Mean serum PSA levels for PET negative and positive groups were 0.76±1.00 and 180.85±324.93 ng/mL (P<0.001). The sensitivity and specificity of 68Ga PSMA PET/CT for detection of disease recurrence were calculated as 92% and 80%, respectively, for the 1.4 ng/mL PSA cut-off and 92% and 90%, respectively, for the 2 ng/mL PSA cut-off values. The positivity rates for patients with PSA levels <1.4 ng/mL and ≥1.4 ng/mL were 21% and 90%, respectively (P<0.001).

CONCLUSIONS

68Ga PSMA PET/CT seems to be a highly sensitive in patients with early PSA recurrence. Patients with higher GS and early PSA recurrence could benefit from 68Ga PSMA PET/CT.

The Utility of PET/CT in the Planning of External Radiation Therapy for Prostate Cancer

Radiotherapy and radical prostatectomy are the definitive treatment options for patients with localized prostate cancer. A rising level of prostate-specific antigen after radical prostatectomy indicates prostate cancer recurrence, and these patients may still be cured with salvage radiotherapy. To maximize chance for cure, the irradiated volumes should completely encompass the extent of disease. Therefore, accurate estimation of the location of disease is critical for radiotherapy planning in both the definitive and the salvage settings. Current first-line imaging for prostate cancer has limited sensitivity for detection of disease both at initial staging and at biochemical recurrence. Integration of PET into routine evaluation of prostate cancer patients may improve both staging accuracy and radiotherapy planning. 18F-FDG PET/CT is now routinely used in radiation planning for several cancer types. However, 18F-FDG PET/CT has low sensitivity for prostate cancer. Additional PET probes evaluated in prostate cancer include 18F-sodium fluoride, 11C-acetate, 11C- or 18F-choline, 18F-fluciclovine, and 68Ga- or 18F-labeled ligands that bind prostate-specific membrane antigen (PSMA). PSMA ligands appear to be the most sensitive and specific but have not yet received Food and Drug Administration New Drug Application approval for use in the United States. Retrospective and prospective investigations suggest a potential major impact of PET/CT on prostate radiation treatment planning. Prospective trials randomizing patients to routine radiotherapy planning versus PET/CT-aided planning may show meaningful clinical outcomes. Prospective clinical trials evaluating the addition of 18F-fluciclovine PET/CT for planning of salvage radiotherapy with clinical endpoints are under way. Prospective trials evaluating the clinical impact of PSMA PET/CT on prostate radiation planning are indicated.

Current application and future perspectives of prostate specific membrane antigen PET imaging in prostate cancer

As precision medicine evolves, the contribution of molecular imaging to the management of prostate cancer (PCa) patients, especially for positron-emission tomography (PET) imaging, is gaining importance. Highly successful approaches to measure the expression of the prostate specific membrane antigen (PSMA) have been introduced recently. PSMA, the glutamate carboxypeptidase II, is a membrane bound metallo-peptidase that is overexpressed in 90-100% of PCa cells. Due to its selective over-expression, PSMA is a reliable tissue marker for prostate cancer and is considered an ideal target for tumor specific imaging and therapy. A variety of PET and SPECT probes targeting this peptide receptor have been introduced. These are undergoing extensive clinical evaluations. Initial results attest to a high accuracy for disease detection compared conventional radiology (CT or MRI) and other nuclear medicine procedure (choline PET or fluciclovine PET). However, prospective evaluation of the impact on patient management for PSMA-ligand PET and its impact on patient outcome is currently missing. Finally, PSMA inhibitors can be radio-labeled with diagnostic (68Ga-PSMA-11), or therapeutic nuclides (177Lu/225Ac PSMA-617) to be used as theranostic agent. Initial results showed that PSMA-targeted radioligand therapy can potentially delay disease progression in metastatic castrate-resistant PCa. This review aims to explore the current application of PSMA based imaging in prostate cancer, reporting about main advantages and limitations of this new theranostic procedure. The future perspectives and potential the applications of this agent will be also discussed.

The use of PET/CT in prostate cancer

BACKGROUND

Positron emission tomography/computed tomography (PET/CT) has recently emerged as a promising diagnostic imaging platform for prostate cancer. Several radiolabelled tracers have demonstrated efficacy for cancer detection in various clinical settings. In this review, we aim to illustrate the diverse use of PET/CT with different tracers for the detection of prostate cancer.

METHODS

We searched MEDLINE using the terms 'prostate cancer', 'PET', 'PET/CT' and 'PET/MR'). The current review was limited to ¹⁸F-NaF PET/CT, choline-based PET/CT, fluciclovine PET/CT and PSMA-targeted PET/CT, as these modalities have been the most widely adopted.

RESULTS

NaF PET/CT has shown efficacy in detecting bone metastases with high sensitivity, but relatively low specificity. Currently, choline PET/CT has been the most extensively studied modality. Although having superior specificity, choline PET/CT suffers from low sensitivity, especially at low PSA levels. Nevertheless, choline PET/CT was found to significantly improve upon conventional imaging modalities (CIM) in the detection of metastatic lesions at biochemical recurrence (BCR). Newer methods using fluciclovine and PSMA-targeted radiotracers have preliminarily demonstrated great promise in primary and recurrent staging of prostate cancer. However, their superior efficacy awaits confirmation in larger series.

CONCLUSIONS

PET/CT has emerged as a promising staging modality for both primary and recurrent prostate cancer. Newer tracers have increased detection accuracies for small, incipient metastatic foci. The clinical implications of these occult PET/CT detected disease foci require organized evaluation. Efforts should be aimed at defining their natural history as well as responsiveness and impact of metastasis-directed therapy.

Contribution of 11C-Choline PET/CT in prostate carcinoma biochemical relapse with serum PSA level below 1 ng/ml

OBJECTIVE

¹¹C-choline PET/CT has demonstrated good results in the restaging of prostate cancer (PCa) with high serum prostate specific antigen (PSA), but its use in patients with low serum PSA is controversial. Our aim was to evaluate the contribution of ¹¹C-choline PET/CT in patients with PCa, biochemical relapse and PSA <1 ng/ml.

MATERIAL AND METHOD

Fifty consecutive patients (mean age: 65.9±5.6 years) with biochemical relapse of PCa and serum PSA <1ng/ml were evaluated retrospectively. PET/CT was performed 20min after intravenous administration of 555-740 MBq of ¹¹C-choline. Minimum follow up time was 30 months.

RESULTS

Twenty-one out of 50 patients (42%) had an abnormal ¹¹C-choline PET/CT. In 7 out of 21 patients (14%) tumor was confirmed (4 in prostatic bed, 4 in pelvic lymph nodes, 2 in mediastinal lymph nodes and one synchronous sigmoid carcinoma), and in all cases the initial therapeutic planning was modified. In 2 patients (4%) subsequent tests diagnosed a benign disease (one sarcoidosis, one tuberculosis sequelae) and in 3 patients (6%) they ruled out pathology. The other 9 patients (18%) had no further assessment (7 mediastinal and 4 pelvic lymph nodes). Twenty-nine out of 50 patients (58%) had a normal PET/CT. At 30 months, follow up recurrence was confirmed only in 2 of these patients.

CONCLUSIONS

¹¹C-choline PET/CT proved its usefulness in demonstrating tumor in 14% of patients with BR of PCa and serum PSA <1ng/ml, with therapeutic implications. In 4% of patients a benign condition was detected. A normal ¹¹C-choline PET/CT was associated with a very low rate of recurrence at 30 months.

Clinical PET Imaging in Prostate Cancer

Prostate cancer is the second most common cancer in men worldwide, with a wide spectrum of biologic behavior ranging from indolent low-risk disease to highly aggressive castration-resistant prostate cancer. Conventional imaging with computed tomography, magnetic resonance imaging, and bone scintigraphy is limited for the detection of nodal disease and distant bone metastases. In addition, advances in the available therapeutic options, both localized and systemic, drive the requirement for precise diagnostic and prognostic tools to refine the individual therapeutic approach at various times in the management of patients with prostate cancer. Positron emission tomography (PET) has a rapidly evolving role in the assessment of prostate cancer, particularly in the scenario of biochemical relapse. Fluorine 18 (¹⁸F) fluorodeoxyglucose, the most widely available PET tracer, has limitations, particularly in indolent prostate cancer. In the past decade, several PET tracers with specific molecular targets have reached the clinical domain. These tracers include ¹⁸F-sodium fluoride, which is a bone-specific biomarker of osteoblastic activity; ¹⁸F-choline and carbon 11-choline, which are directed at cell membrane metabolism; gallium 68-prostate-specific membrane antigen ligands; and, more recently, an amino acid analog, ¹⁸F-fluciclovine (anti-1-amino-3-¹⁸F-fluorocyclobutane-1-carboxylic acid; also known as FACBC), which is also directed at cell membrane turnover. The mechanisms of actions of the clinically available PET tracers are reviewed, as well as their role in the imaging of prostate cancer with reference to relevant guidelines and the technical and imaging pearls and pitfalls of these tracers. ^©RSNA, 2017.