Is there a diagnostic benefit of late-phase abdomino-pelvic PET/CT after urination as part of whole-body 68 Ga-PSMA-11 PET/CT for restaging patients with biochemical recurrence of prostate cancer after radical prostatectomy?

The evolution of PET imaging in renal, bladder, upper urinary tract urothelial, testicular and penile carcinoma - Today's impact, tomorrow's potential

INTRODUCTION

The advancement of hybrid PET/CT or PET/MRI imaging for non-prostate genitourinary cancers has not experienced the rapid progress of prostate cancer. Nevertheless, these neoplasms are aggressive and reliable imaging plays a pivotal role in enhancing patients' quality of life and prognosis.

AREAS COVERED

the main evidence regarding [18F]FDG and non-[18F]FDG PET/CT or PET/MRI in non-prostate uro-oncological malignancies are summarized and discussed. Moreover, potential future directions concerning PET imaging in these neoplasms are debated, with the aim to stimulate future research projects covering these fields.

EXPERT OPINION

In Renal Cell Carcinoma (RCC), [18F]FDG PET/CT demonstrates varying efficacy in staging, restaging, and prognostic stratification, but PSMA PET/CT is emerging as a potential game-changer, particularly in advanced, high-grade aggressive clear cell RCC. [18F]FDG PET/CT may see an increased use in N and M-staging of bladder cancer, as well as for detecting recurrence and response to neoadjuvant chemotherapy. Preliminary data regarding [68Ga]-FAPI also looks promising in this context. [18F]FDG PET/MRI could be useful for the T-staging of bladder cancer, while upper tract urothelial carcinoma still lacks of molecular imaging literature reports. In testicular and penile cancer [18F]FDG PET/CT has demonstrated its usefulness in several clinical settings, although experiences with non-[18F]FDG radiotracers are lacking.

What should be the future direction of development in the field of prostate cancer with lung metastasis?

BACKGROUND

Since the start of the 21st century, prostate cancer with lung metastasis (PCLM) has accumulated significant scientific research output. However, a systematic knowledge framework for PCLM is still lacking.

AIM

To reconstruct the global knowledge system in the field of PCLM, sort out hot research directions, and provide reference for the clinical and mechanism research of PCLM.

METHODS

We retrieved 280 high-quality papers from the Web of Science Core Collection and conducted a bibliometric analysis of keywords, publication volume, and citation frequency. Additionally, we selected differentially expressed genes from global high-throughput datasets and performed enrichment analysis and protein-protein interaction analysis to further summarize and explore the mechanisms of PCLM.

RESULTS

PCLM has received extensive attention over the past 22 years, but there is an uneven spatial distribution in PCLM research. In the clinical aspect, the treatment of PCLM is mainly based on chemotherapy and immunotherapy, while diagnosis relies on methods such as prostate-specific membrane antigen positron emission tomography/computed tomography. In the basic research aspect, the focus is on cell adhesion molecules and signal transducer and activator of transcription 3, among others. Traditional treatments, such as chemotherapy, remain the mainstay of PCLM treatment, while novel approaches such as immunotherapy have limited effectiveness in PCLM. This study reveals for the first time that pathways related to coronavirus disease 2019, cytokine-cytokine receptor interaction, and ribosome are closely associated with PCLM.

CONCLUSION

Future research should focus on exploring and enhancing mechanisms such as cytokine-cytokine receptor interaction and ribosome and improve existing mechanisms like cadherin binding and cell adhesion molecules.

Combined forced diuresis and late acquisition on [68Ga]Ga-PSMA-11 PET/CT for biochemical recurrent prostate cancer: a clinical practice-oriented study

OBJECTIVES

Increased detection of prostate cancer (PCa) recurrences using [⁶⁸Ga]Ga-PSMA-11 PET/CT has been reported by adding forced diuresis or late-phase imaging to the standard protocol. However, the combination of these procedures in the clinical setting is still not standardized.

METHODS

One hundred prospectively recruited biochemical recurrent PCa patients were restaged with dual-phase [⁶⁸Ga]Ga-PSMA-11 PET/CT from September 2020 to October 2021. All patients received a standard scan (60 min), followed by diuretics (140 min) and a late-phase abdominopelvic scan (180 min). PET readers with low (n = 2), intermediate (n = 2), or high (n = 2) experience rated (i) standard and (ii) standard + forced diuresis late-phase images in a stepwise fashion according to E-PSMA guidelines, scoring their level of confidence. Study endpoints were (i) accuracy against a composite reference standard, (ii) reader's confidence level, and (iii) interobserver agreement.

RESULTS

Forced diuresis late-phase imaging increased the reader's confidence category for local and nodal restaging (both p < 0.0001), and the interobserver agreement in identifying nodal recurrences (from moderate to substantial, p < 0.01). However, it significantly increased diagnostic accuracy exclusively for local uptakes rated by low-experienced readers (from 76.5 to 84%, p = 0.05) and for nodal uptakes rated as uncertain at standard imaging (from 68.1 to 78.5%, p < 0.05). In this framework, SUVmax kinetics resulted in an independent predictor of PCa recurrence compared to standard metrics, potentially guiding the dual-phase PET/CT interpretation.

CONCLUSIONS

The present results do not support the systematic combination of forced diuresis and late-phase imaging in the clinical setting, but allow the identification of patients-, lesions-, and reader-based scenarios that might benefit from it.

KEY POINTS

• Increased detection of prostate cancer recurrences has been reported by adding diuretics administration or an additional late abdominopelvic scan to the standard [⁶⁸Ga]Ga-PSMA-11 PET/CT procedure. • We verified the added value of combined forced diuresis and delayed imaging, showing that this protocol only slightly increases the diagnostic accuracy of [⁶⁸Ga]Ga-PSMA-11 PET/CT, thus not justifying its systematic use in clinics. • However, it can be helpful in specific clinical scenarios, e.g., when PET/CT is reported by low-experienced readers. Moreover, it increased the reader's confidence and the agreement among observers.

Preclinical evaluation and first in human study of Al18F radiolabeled ODAP-urea-based PSMA targeting ligand for PET imaging of prostate cancer

PURPOSE

This study aimed to introduce a novel [18F]AlF-labeled ODAP-Urea-based Prostate-specific membrane antigen (PSMA) probe, named [18F]AlF-PSMA-137, which was derived from the successful modification of glutamate-like functional group. The preclinically physical and biological characteristics of the probe were analyzed. Polit clinical PET/CT translation was performed to analyze its feasibility in clinical diagnosis of prostate cancer.

METHODS

[18F]AlF-PSMA-137 was maturely labeled with the [18F]AlF2+ labeling technique. It was analyzed by radio-HPLC for radiochemical purity and stability analysis in vitro and in vivo. The PSMA specificity was investigated in PSMA-positive (LNCaP) and PSMA-negative (PC3) cells, and the binding affinity was evaluated in LNCaP cells. Micro-PET/CT imaging was performed in mice bearing LNCaP or PC3 tumors. Thirteen patients with newly diagnosed prostate cancer were included for [18F]AlF-PSMA-137 PET/CT imaging. Physiologic biodistribution and tumor burden were semi-quantitatively evaluated and the radiation dosimetry of [18F]AlF-PSMA-137 was estimated.

RESULTS

The radiochemical yield of [18F]AlF-PSMA-137 was 54.2 ± 10.7% (n = 16) with the radiochemical purity over 99% and the specific activity of 26.36 ± 7.33 GBq/μmol. The binding affinity to PSMA was 2.11 ± 0.63 nM. [18F]AlF-PSMA-137 showed high cell/tumor uptake which can be specifically blocked by PSMA inhibitor. According to the biodistribution in patients, [18F]AlF-PSMA-137 was mainly accumulated in kidneys, lacrimal glands, parotid glands, submandibular glands and liver which was similar to the extensive Glu-Ureas based probes. A total of 81 lesions were detected in PET/CT imaging and over 91% of lesions increased between 1 h p.i. (SUVmean: 10.98 ± 18.12) and 2 h p.i. (SUVmean: 14.25 ± 21.28) (p < 0.001). Additionally, the probe showed intensive accumulation in lesions which provided excellent imaging contrast with the high tumor-to-muscle ratio of 15.57 ± 27.21 at 1 h p.i. and 25.42 ± 36.60 at 2 h p.i. (p < 0.001), respectively. The effective dose of [18F]AlF-PSMA-137 was estimated as 0.0119 ± 0.0009 mSv/MBq.

CONCLUSION

An ODAP-Urea-based PSMA probe [18F]AlF-PSMA-137 was successfully prepared with high specificity and binding affinity to PSMA. Micro-PET/CT imaging study demonstrated its feasibility for prostate cancer imaging. Pilot clinical study showed its potential for delay-imaging and prostate cancer detection.

Evaluation of [68 Ga]Ga-PSMA-I&T PET/CT with additional late scans of the pelvis in prostate-specific antigen recurrence using the PROMISE criteria

Background

PSMA PET/CT is the recommended imaging test in cases with prostate-specific antigen (PSA) recurrence after primary therapy of prostate cancer (PCa). However, imaging protocols remain a topic of active research. The aim of the presented study was to examine the impact of additional late scans of the pelvis in [⁶⁸ Ga]Ga-PSMA-I&T PET/CT of patients with rising PSA after prostatectomy.

Methods

A total of 297 patients (median PSA 0.35 ng/ml, interquartile range (IQR) 0.2–0.8) who underwent early whole-body [⁶⁸ Ga]Ga-PSMA-I&T PET/CT (median dose 141 MBq, IQR 120–163; median 86 min, IQR 56–107) and additional late scans of the pelvis (median 180 min, IQR 170–191) were investigated retrospectively. Early and late images were staged separately according to the PROMISE criteria and compared with a final consensus of both. Standardized uptake values were analyzed for early and late scans.

Results

One hundred and thirty-four (45.1%) [⁶⁸ Ga]Ga-PSMA-I&T PET/CT showed evidence of recurrent PCa (114/38.4% early, 131/44.1% late). Of 195 lesions, 144 (73.8%) were identified correctly on early scans. 191 (97.9%) lesions were detected on late imaging. The lesion SUVmax (median 3.4, IQR 0.4–6.5 vs. median 3.9, IQR 2.6–8.2) as well as the SUVmax to background ratio (median 9.4, IQR 1.7–19.1 vs. median 15.5, IQR 9.6–34.1) increased significantly between the imaging time points (p < 0.01, respectively). Compared to the final consensus, the miTNM-staging of early scans changed in 58 (19.5%) cases. Of these, 31 patients (10.4%) with negative early scans (T0 N0 M0) were upstaged. Twenty-seven (9.1%) patients with PCa characteristic lesions on early imaging (> T0 N0 M0) were up- and/or downstaged. In 4 (1.3%) cases, PCa-related lesions were only detectable on early PET/CT leading to upstagings of late imaging.

Conclusions

Additional late scans of the pelvis in [⁶⁸ Ga]Ga-PSMA-I&T PET/CT detected more lesions and an increasing contrast compared to early imaging. This influenced the final miTNM-staging substantially.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13550-022-00938-3.

The future of PSMA PET and WB MRI as next-generation imaging tools in prostate cancer

Radiolabelled prostate-specific membrane antigen (PSMA)-based PET-CT has been shown in numerous studies to be superior to conventional imaging in the detection of nodal or distant metastatic lesions. ⁶⁸Ga-PSMA PET-CT is now recommended by many guidelines for the detection of biochemically relapsed disease after radical local therapy. PSMA radioligands can also function as radiotheranostics, and Lu-PSMA has been shown to be a potential new line of treatment for metastatic castration-resistant prostate cancer. Whole-body (WB) MRI has been shown to have a high diagnostic performance in the detection and monitoring of metastatic bone disease. Prospective, randomized, multicentre studies comparing ⁶⁸Ga-PSMA PET-CT and WB MRI for pelvic nodal and metastatic disease detection are yet to be performed. Challenges for interpretation of PSMA include tracer trapping in non-target tissues and also urinary excretion of tracers, which confounds image interpretation at the vesicoureteral junction. Additionally, studies have shown how long-term androgen deprivation therapy (ADT) affects PSMA expression and could, therefore, reduce tracer uptake and visibility of PSMA⁺ lesions. Furthermore, ADT of short duration might increase PSMA expression, leading to the PSMA flare phenomenon, which makes the accurate monitoring of treatment response to ADT with PSMA PET challenging. Scan duration, detection of incidentalomas and presence of metallic implants are some of the major challenges with WB MRI. Emerging data support the wider adoption of PSMA PET and WB MRI for diagnosis, staging, disease burden evaluation and response monitoring, although their relative roles in the standard-of-care management of patients are yet to be fully defined.

The Value of Multimodality PET/CT Imaging in Detecting Prostate Cancer Biochemical Recurrence

Prostate cancer (PCa) induced death is the predominant cause of cancer-related death among men in 48 countries. After radical treatment, biochemical recurrence has become an important factor for prognosis. The early detection and diagnosis of recurrent lesions are very helpful in guiding treatment and improving the prognosis. PET/CT is a promising method for early detection of lesions in patients with biochemical recurrence of prostate cancer. This article reviews the progress of the research on PET/CT in the PCa biochemical recurrence and aims to introduce new technologies and provide more direction for future research.