The use of 68Ga-PET/CT PSMA in the staging of primary and suspected recurrent renal cell carcinoma

Utility of PSMA PET/CT in Staging and Restaging of Renal Cell Carcinoma: A Systematic Review and Metaanalysis

Prostate-specific membrane antigen (PSMA) is expressed in the neovasculature of multiple solid tumors, including renal cell carcinoma (RCC). Studies have demonstrated promising results on the utility of PSMA-targeted PET/CT imaging in RCC. This report aims to provide a systematic review and metaanalysis on the utility and detection rate of PSMA PET/CT imaging in staging or evaluation of primary RCC and restaging of metastatic or recurrent RCC. Methods: Searches were performed in PubMed, Embase, and abstract proceedings (last updated, August 2023). Studies that provided a lesion-level detection rate of PSMA radiotracers in staging or restaging of RCC were included in the metaanalysis. The overall pooled detection rate with a 95% CI was estimated, and subgroup analysis was performed when feasible. Results: Nine studies comprising 152 patients (133 clear cell RCC [ccRCC], 19 other RCC subtypes) were included in the metaanalysis. The pooled detection rate of PSMA PET/CT in evaluation of primary or metastatic RCC was estimated to be 0.83 (95% CI, 0.67-0.92). Subgroup analysis showed a pooled PSMA detection rate of 0.74 (95% CI, 0.57-0.86) in staging or evaluation of primary RCC lesions and 0.87 (95% CI, 0.73-0.95) in restaging of metastatic or recurrent RCC. Analysis based on the type of radiotracer showed a pooled detection rate of 0.85 (95% CI, 0.62-0.95) for 68Ga-based PSMA tracers and 0.92 (95% CI, 0.76-0.97) for 18F-DCFPyL PET/CT. Furthermore, in metastatic ccRCC, the available data support a significantly higher detection rate for 18F-DCFPyL PET/CT than for conventional imaging modalities (2 studies). Conclusion: Our preliminary results show that PSMA PET/CT could be a promising alternative imaging modality for evaluating RCC, particularly metastatic ccRCC. Large prospective studies are warranted to confirm clinical utility in the staging and restaging of RCC.

PET/Computed Tomography Transformation of Oncology: Kidney and Urinary Tract Cancers

Renal cell carcinoma (RCC) and urothelial carcinoma (UC) are two of the most common genitourinary malignancies. 2-deoxy-2-[18F]fluoro-d-glucose (18F-FDG) can play an important role in the evaluation of patients with RCC and UC. In addition to the clinical utility of 18F-FDG PET to evaluate for metastatic RCC or UC, the shift in molecular imaging to focus on specific ligand-receptor interactions should provide novel diagnostic and therapeutic opportunities in genitourinary malignancies. In combination with the rise of artificial intelligence, our ability to derive imaging biomarkers that are associated with treatment selection, response assessment, and overall patient prognostication will only improve.

The results of surgery for renal cell carcinoma metastases of the pancreas

BACKGROUND

Pancreatic metastases from renal cell carcinoma (RCC) are rare. This study evaluated the surgical pathology and outcomes after resection of RCC metastases to the pancreas.

MATERIAL AND METHODS

A retrospective review of from 1 January 2011 to 31 December 2021, of patients who underwent pancreatic surgery for metastases from RCC. Data were retrieved from a prospectively managed database and patient demographics, comorbidities, pathology, perioperative outcomes, and overall survival were analyzed. Median overall survival (OS) and disease-free survival (DFS) were estimated by the Kaplan-Meier method.

RESULTS

There were 25 patients (17 males, 8 females, median age 66 range 51 - 79 year), all with metachronous metastases. Median time from resection of the primary to operation for pancreatic RCC was 95.6 (12.0 - 309.7) months. Twenty-four patients were operated with intended cure (four pancreaticoduodenectomies, three total pancreatectomies, 17 distal pancreatectomies) and one patient had abortive surgery due to dissemination. Postoperative surgical complications occurred in nine patients (36%), and one patient died during hospital stay. Eight patients (33.3%) developed exocrine and/or endocrine insufficiency after pancreatic resection. Fifteen patients (60%) had recurrence 21.7 (4.9 - 61.6) months after pancreatic operation. Five patients (25%) died from RCC during follow-up 46.3 (25.6 - 134.8) months after pancreatic resection. Five-year OS and DFS were83.6% and 32.3%, respectively. Median OS after pancreatic surgery was 134.8 months, independent of resection of previous extrapancreatic metastases.

CONCLUSIONS

Pancreatic resection for metastases from RCC offers favorable prognosis with a curative potential and should be considered a valuable treatment option even in the era of novel targeted treatment.

Role of PSMA-targeted PET-CT in renal cell carcinoma: a systematic review and meta-analysis

Fluoro-deoxy glucose positron emission tomography/computed tomography (PET/CT), the workhorse of nuclear medicine, has limited utility for renal cell carcinoma (RCC), particularly clear cell variant. Thus, various other tracers have been tried for evaluation of RCC. One of the most promising targets for radiotracers is prostate-specific membrane antigen (PSMA) expressed in abundance in carcinoma-associated neo-vasculature. Thus, we tried to review and analyse the role of PSMA-targeted PET/CT in evaluation of RCC. Databases like PubMed, EMBASE and SCOPUS were searched for original studies published on PSMA-targeted PET/CT in RCC till 30 September 2023. Revised Tool for the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) checklist was used to assess the included studies. Pooled sensitivity and specificity were calculated and represented with 95% confidence intervals (95%CI). Heterogeneity in the studies was assessed by I-square index. Pooled sensitivity and specificity of PSMA-targeted PET/CT for detection of local disease estimates were 87.2% (95%CI: 77-94%) and 100% (95%CI: 92.9-100%), respectively. Pooled sensitivity and specificity for detection of local recurrent disease are 100% (95%CI: 71.5-100%) and 100% (95%CI: 89.4-100%), respectively. Pooled sensitivity and specificity for detection of metastatic disease are 92% (95%CI: 86.2-96%) and 96.9% (95%CI: 83.8-99.9%), respectively. Pooled sensitivity of PSMA-targeted PET/CT for detection of clear cell renal cell carcinoma (ccRCC) and non-ccRCC are 94.7% (95%CI: 88-98.3%) and 75% (95%CI: 35-96.8%), respectively. PSMA-targeted PET-CT demonstrated better diagnostic efficacy for the detection of recurrent RCC. Whilst for staging RCC, it had higher specificity but lower sensitivity. Thus, it can serve as a non-invasive adjuvant tool to conventional imaging in the evaluation of staging of RCC, particularly clear cell variant.

A multicentric, single arm, open-label, phase I/II study evaluating PSMA targeted radionuclide therapy in adult patients with metastatic clear cell renal cancer (PRadR)

BACKGROUND

Despite advancements in managing metastatic clear cell renal carcinoma (mccRCC) through antiangiogenic tyrosine kinase inhibitors and immunotherapy, there remains a demand for novel treatments for patients experiencing progression despite the use of these medications. There is currently no established standard treatment for patients receiving third therapy line. Prostate Specific Membrane Antigen (PSMA) whose high expression has been demonstrated in metastatic aggressive prostate adenocarcinoma is also highly expressed in neovessels of various solid tumors including renal cell carcinoma (RCC): 86% of clear cell RCC, 61% of chromophobe RCC, and 28% of papillary RCC. Therefore, PSMA may be a target expressed in metastatic ccRCC for radionuclide therapy using PSMA ligands radiolabeled with Lutetium-177 (PRLT). 177Lu-PSMA delivers ß-particle radiation to PSMA-expressing cells and the surrounding microenvironment with demonstrated efficacy in metastatic prostate cancer.

METHODS

This is a multicenter phase I/II study designed to assess the tolerability and effectiveness of 177Lu-PSMA-1 in individuals with PSMA-positive metastatic clear cell renal cell carcinoma (ccRCC), identified through 68Ga-PSMA PET, conducted in France (PRadR). 48 patients will be treated with 4 cycles of 7.4 GBq of 177Lu-PSMA-1 every 6 weeks. The primary objective is to evaluate the safety of 177Lu-PSMA-1 (phase I) and the efficacy of 177Lu-PSMA-1 in mccRCC patients (phase II). Primary endpoints are incidence of Severe Toxicities (ST) occurring during the first cycle (i.e. 6 first weeks) and disease Control Rate after 24 weeks of treatment (DCR24w) as per RECIST V1.1. Secondary objective is to further document the clinical activity of 177Lu-PSMA-1 in mccRCC patients (duration of response (DoR), best overall response rate (BORR), progression fee survival (PFS) and overall survival (OS).

DISCUSSION

Our prospective study may lead to new potential indications for the use of 177Lu-PSMA-1 in mccRCC patients and should confirm the efficacy and safety of this radionuclide therapy with limited adverse events. The use of 177Lu-PSMA-1may lead to increase disease control, objective response rate and the quality of life in mccRCC patients.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT06059014.

The Role of Prostate-specific Membrane Antigen Positron Emission Tomography/Computed Tomography in Primary Staging of Selected Renal Tumours: Initial Experience in a Multicentre Cohort

BACKGROUND

Accurate primary staging of renal cancer with conventional imaging is challenging. Prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) may serve to improve the accuracy of renal cancer staging.

OBJECTIVE

To determine clinicopathological and management differences for primary renal cancer staged with PSMA PET/CT in comparison to conventional imaging.

DESIGN, SETTING, AND PARTICIPANTS

We conducted a retrospective cohort study of PSMA PET/CT scans performed for primary staging of renal cancer and incidental renal lesions at three sites in Brisbane, Australia between June 2015 and June 2020. Clinical characteristics, imaging, and histopathology were reviewed.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Clinicopathological and management differences according to staging modality (PSMA PET/CT, conventional imaging) were assessed. Descriptive statistics were used to report demographics and clinical parameters. Nonparametric methods were used for statistical analysis. Fisher's exact test was used for comparison of small-cell size categorical variables.

RESULTS AND LIMITATIONS

From a total of 120 PSMA PET/CT scans, 61 were included (52 staging, 9 incidental) for predominantly males (74%) with a mean age of 65.1 yr (standard deviation 12.0). Most primary lesions (40/51) were clear-cell renal cell carcinoma (ccRCC; 98% PSMA-avid), eight were non-ccRCC (75% PSMA-avid), and three were non-RCC (oncocytoma; 67% PSMA-avid). PSMA PET identified a greater number of presumed metastatic lesions than conventional imaging (195 vs 160). A management change was observed for 32% of patients (20% major, 12% minor). Limitations include the retrospective design and selection bias, lack of blinding to PSMA reporting, and the use of different PSMA radiotracers.

CONCLUSIONS

PSMA PET/CT detected more metastases than conventional imaging and most renal cancers were PSMA-avid, resulting in a management change for one-third of the patients.

PATIENT SUMMARY

We looked at a newer type of scan called PSMA PET/CT for first staging of kidney cancer. We found that this detects more metastasis and helps in decisions on changes in treatment for some patients. This type of imaging is a useful addition to conventional scans in tricky cases and may help in better selection of suitable treatments, but more studies are required.

Potential role of 68Ga-PSMA PET/CT in metastatic renal cell cancer: A prospective study

PURPOSE

Prostate-specific membrane antigen (PSMA), in addition to its utility in prostate cancer, is also an angiogenic imaging marker for hypervascular tumors like renal cell carcinoma (RCC). Our study aims to assess the potential role of 68Ga-PSMA-11 positron emission tomography (PET)/CT in metastatic RCC and compare it with contrast-enhanced computed tomography (CECT).

METHODS

Biopsy-proven RCC patients with known or suspected distant metastases who underwent 68Ga-PSMA-11 PET/CT for staging/restaging were prospectively recruited. Those patients who had undergone 18F-FDG PET/CT within six weeks of 68Ga-PSMA PET/CT were also included retrospectively for comparative analysis. A patient-based and lesion-based analysis was done to compare the lesion detection rates of CECT, 68Ga-PSMA-11 PET and 18F-FDG PET. PET-based quantitative parameters were also compared between both the PET modalities. Impact of baseline parameters on survival was assessed using Cox regression analysis. A p-value of < 0.05 was considered significant.

RESULTS

Thirty-seven patients with median age 60 years ± 13 years (range = 26-76 years) were included in the study. Twenty-seven patients had clear cell (cc) RCC, six had papillary RCC (pRCC), and one each had an eosinophilic variant of ccRCC, collecting duct RCC, translocation RCC and poorly differentiated RCC. 68Ga-PSMA-11 PET performed better in detecting marrow and equivocal bone lesions and worse in detecting liver lesions compared to CECT. 68Ga-PSMA-11 PET-based angiogenic tumor burden estimation using Total Lesion-PSMA (TL-PSMA) and PSMA-Total volume (PSMA-TV) had a prognostic impact on the survival of patients. 68Ga-PSMA-11 PET also detected more lesions and showed significantly higher SUVmax than 18F-FDG PET.

CONCLUSION

68Ga-PSMA-11 PET/CT performs better than CECT and 18F-FDG PET/CT in metastatic evaluation and has prognostic value in the management of clear cell RCC.

A Practical Guide to the Pearls and Pitfalls of PSMA PET Imaging

Prostate-specific membrane antigen (PSMA)-targeted PET agents have revolutionized the care of patients with prostate cancer, supplanting traditional methods of imaging prostate cancer, and improving the selection and delivery of therapies. This has led to a rapid expansion in both the number of PSMA PET scans performed and the imaging specialists required to interpret those scans. To aid those imagers and clinicians who are new to the interpretation of PSMA PET, this review provides an overview of the interpretation of PSMA PET/CT imaging and pearls for overcoming commonly encountered pitfalls. We discuss the physiologic distribution of the clinically available PSMA-targeted radiotracers, the commonly encountered patterns of prostate cancer spread, as well as the benign and malignant mimics of prostate cancer. Additionally, we review the standardized PSMA PET reporting systems and the role of PSMA in selecting appropriate patients for PSMA-targeted therapies.

Tata Memorial Centre Evidence Based Use of Nuclear medicine diagnostic and treatment modalities in cancer

ABSTRACT

PET/CT and radioisotope therapy are diagnostic and therapeutic arms of Nuclear Medicine, respectively. With the emergence of better technology, PET/CT has become an accessible modality. Diagnostic tracers exploring disease-specific targets has led the clinicians to look beyond FDG PET. Moreover, with the emergence of theranostic pairs of radiopharmaceuticals, radioisotope therapy is gradually making it's way into treatment algorithm of common cancers in India. We therefore would like to discuss in detail the updates in PET/CT imaging and radionuclide therapy and generate a consensus-driven evidence based document which would guide the practitioners of Oncology.

[68Ga]Ga‑LNC1007 PET/CT in the evaluation of renal cell carcinoma: comparison with 2-[18F]FDG/[68Ga]Ga-PSMA PET/CT

PURPOSE

To compare the potential efficiency of [68Ga]Ga-LNC1007 with 2-[18F]FDG/[68Ga]Ga-PSMA PET/CT for detecting renal cell carcinoma (RCC) and to explore parameters derived from [68Ga]Ga-LNC1007 PET/CT for discriminating pathological characteristics in RCC.

METHODS

Twenty-five RCC patients confirmed by pathology were enrolled in this prospective study. The maximum standardized uptake value (SUVmax), mean SUV (SUVmean), gross tumor volume (GTV) and total lesion-tracer (TL-tracer) of lesions were calculated from the corresponding PET/CT images. Pathological characteristics included World Health Organization/International Society of Urological Pathology (WHO/ISUP) grade and adverse pathological features (tumor necrosis or sarcomatoid or rhabdoid feature).

RESULTS

[68Ga]Ga-LNC1007 PET/CT showed a higher detection rate for primary lesions than 2-[18F]FDG and [68Ga]Ga-PSMA (LNC1007 vs. FDG: 13/17 vs. 4/17, P = 0.005; LNC1007 vs. PSMA: 9/11 vs. 6/11, P = 0.361). [68Ga]Ga-LNC1007 PET/CT showed higher SUVmax (6.6 vs. 3.7, P = 0.005), SUVmean (4.1 vs. 2.3, P = 0.001) and TBR (2.6 vs. 1.7, P = 0.011) compared with 2-[18F]FDG PET/CT, and it also showed higher TBR (2.9 vs. 0.5, P = 0.003), TBR-delay (2.8 vs. 0.3, P = 0.003), GTV (84.1 vs. 42.9, P = 0.003) and TL-tracer (442.7 vs. 235.8, P = 0.008) compared with [68Ga]Ga-PSMA PET/CT. SUVmax and TBR derived from [68Ga]Ga-LNC1007 PET/CT could effectively differentiate WHO/ISUP grade (3-4 vs. 1-2) and adverse pathological features (positive vs. negative) (SUVmax: AUC 0.81, P = 0.04; AUC 0.80, P = 0.033; TBR: AUC 0.84, P = 0.026; AUC 0.85, P = 0.014). The SUVmax was positively correlated with the FAP expression, integrin αvβ3 expression and the total expression of FAP and integrin αvβ3 (r = 0.577, P = 0.006, r = 0.701, P < 0.001, and r = 0.702, P < 0.001, respectively).

CONCLUSION

[68Ga]Ga-LNC1007 is a promising tracer for RCC imaging and can effectively identify aggressive pathological characteristics of RCC.

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.

Synchronous Colorectal and Prostate Cancer: Dual PET/CT Approach for Detecting and Distinguishing Metastatic Patterns

Prostate cancer (PC) and colorectal cancer (CRC) are two of the leading causes of cancer-related mortality. The incidence of synchronous neoplasms in patients with CRC is increasing, though synchronous PC and CRC remains a rare occurrence in clinical practice. Early diagnosis, accurate staging, and characterization of tumors are essential for selecting patient-tailored therapy. The origin of metastatic disease in synchronous cases presents a challenge for conventional imaging modalities, but advances in molecular imaging have addressed this limitation. Positron emission tomography/computed tomography (PET/CT) is now the preferred modality for assessing synchronous cases. The authors present a 72-year-old male patient with the rare occurrence of two coexisting primary cancers. At first, fluorine-18 fluorodeoxyglucose (18F-FDG) PET/CT detected the first colorectal primary tumor extension along with evidence of heterogeneous 18F-FDG activity within an enlarged prostate, warranting further evaluation. Subsequently, gallium-68 prostate-specific membrane antigen (68 Ga-PSMA) PET/CT imaging revealed the second prostate primary cancer with evidence of bone metastases. Adoption of a dual PET/CT approach in cases where biopsy is impractical can achieve accurate staging results during the initial diagnostic workup.

68 Ga-LNC-1007 PET/CT Imaging in a Patient With Renal Cell Carcinoma Compared With 68 Ga-PSMA-11 PET/CT

ABSTRACT

A 57-year-old man was incidentally found with 3 lesions located in bilateral kidneys, which were finally diagnosed as renal cell carcinoma (RCC) by postoperative pathology. 68 Ga-LNC-1007, also denoted as 68 Ga-FAPI-RGD, was synthesized from fibroblast activation protein inhibitor-02 (FAPI-02) and cyclic arginine-glycine-aspartate (RGD), which could target both FAP and integrin α v β 3 . RCC lesions demonstrated only slight 68 Ga-PSMA uptake, but intense tracer uptake on 68 Ga-LNC-1007 PET/CT. This case demonstrates the potential value of 68 Ga-LNC-1007 PET/CT for the evaluation of RCC.

PSMA-Expression Is Highly Associated with Histological Subtypes of Renal Cell Carcinoma: Potential Implications for Theranostic Approaches

In renal cell carcinoma (RCC), accurate imaging methods are required for treatment planning and response assessment to therapy. In addition, there is an urgent need for new therapeutic options, especially in metastatic RCC. One way to combine diagnostics and therapy in a so-called theranostic approach is the use of radioligands directed against surface antigens. For instance, radioligands against prostate-specific membrane antigen (PSMA) have already been successfully used for diagnosis and radionuclide therapy of metastatic prostate cancer. Recent studies have demonstrated that PSMA is expressed not only in prostate cancer but also in the neovasculature of several solid tumors, which has raised hopes to use PSMA-guided theranostic approaches in other tumor entities, too. However, data on PSMA expression in different histopathological subtypes of RCC are sparse. Because a better understanding of PSMA expression in RCC is critical to assess which patients would benefit most from theranostic approaches using PSMA-targeted ligands, we investigated the expression pattern of PSMA in different subtypes of RCC on protein level. Immunohistochemical staining for PSMA was performed on formalin-fixed, paraffin-embedded archival material of major different histological subtypes of RCC (clear cell RCC (ccRCC)), papillary RCC (pRCC) and chromophobe RCC (cpRCC). The extent and intensity of PSMA staining were scored semi-quantitatively and correlated with the histological RCC subtypes. Group comparisons were calculated with the Kruskal-Wallis test. In all cases, immunoreactivity was detected only in the tumor-associated vessels and not in tumor cells. Staining intensity was the strongest in ccRCC, followed by cpRCC and pRCC. ccRCC showed the most diffuse staining pattern, followed by cpRCC and pRCC. Our results provide a rationale for PSMA-targeted theranostic approaches in ccRCC and cpRCC.

Insights into Renal Cell Carcinoma with Novel Imaging Approaches

This article presents a comprehensive overview of new imaging approaches and techniques for improving the assessment of renal masses and renal cell carcinoma. The Bosniak classification, version 2019, as well as the clear cell likelihood score, version 2.0, will be discussed as new imaging algorithms using established techniques. Additionally, newer modalities, such as contrast-enhanced ultrasound, dual energy computed tomography, and molecular imaging, will be discussed in conjunction with emerging radiomics and artificial intelligence techniques. Current diagnostic algorithms combined with newer approaches may be an effective way to overcome existing limitations in renal mass and RCC characterization.

High Prognostic Value of 68Ga-PSMA PET/CT in Renal Cell Carcinoma and Association with PSMA Expression Assessed by Immunohistochemistry

In oligo-metastatic renal cell carcinoma (RCC), neither computed tomography (CT) nor bone scan is sensitive enough to detect small tumor deposits hampering early treatment and potential cure. Prostate-specific membrane antigen (PSMA) is a transmembrane glycoprotein expressed in the neo-vasculature of numerous malignant neoplasms, including RCC, that can be targeted by positron emission tomography (PET) using PSMA-targeting radioligands. Our aim was to investigate whether PSMA-expression patterns of renal cancer in the primary tumor or metastatic lesions on immunohistochemistry (IHC) are associated with PET/CT findings using [68Ga]-PSMA-HBED-CC (PSMA-PET/CT). We then analyzed the predictive and prognostic role of the PSMA-PET/CT signal. In this retrospective single-center study we included patients with renal cancer submitted to PSMA-PET/CT for staging or restaging, with tumor specimens available for PSMA-IHC. Clinical information (age, tumor type, and grade) and IHC results from the primary tumor or metastases were collected. The intensity of PSMA expression at IHC was scored into four categories: 0: none; 1: weak; 2: moderate; 3: strong. PSMA expression was also graded according to the proportion of vessels involved (PSMA%) into four categories: 0: none; 1: 1-25%; 2: 25-50%; 3: >50%. The intensity of PSMA expression and PSMA% were combined in a three-grade score: 0-2 absent or mildly positive, 3-4 moderately positive, and 5-6 strongly positive. PSMA scores were used for correlation with PSMA-PET/CT results. Results: IHC and PET scans were available for the analysis in 26 patients (22 ccRCC, 2 papillary RCC, 1 chromophobe, 1 "not otherwise specified" RCC). PSMA-PET/CT was positive in 17 (65%) and negative in 9 patients (35%). The mean and median SUVmax in the target lesion were 34.1 and 24.9, respectively. Reporter agreement was very high for both distant metastasis location and local recurrence (kappa 1, 100%). PSMA-PET detected more lesions than conventional imaging and revealed unknown metastases in 4 patients. Bone involvement, extension, and lesion number were greater than in the CT scan (median lesion number on PET/CT 3.5). The IHC PSMA score was concordant in primary tumors and metastases. All positive PSMA-PET/CT results (15/22 ccRCC, 1 papillary cancer type II, and 1 chromofobe type) were revealed in tumors with strong or moderate PSMA combined scores (3-4 and 5-6). In ccRCC tissue samples, PSMA expression was strong to moderate in 20/22 cases. The SUVmax values correlated to the intensity of PSMA expression which were assessed using IHC (p = 0.01), especially in the ccRCC subgroup (p = 0.009). Median survival was significantly higher in patients with negative PSMA-PET/CT (48 months) compared to patients with a positive scan (24 months, p= 0.001). SUVmax ≥ 7.4 provides discrimination of patients with a poor prognosis. Results of PSMA-PET/CT changed treatment planning. Conclusions: in renal cancer, positive PSMA-PET/CT is strongly correlated to the intensity of PSMA expression on immunohistochemistry in both ccRCC and chromophobe cancer. PSMA-PET/CT signal predicts a poor prognosis confirming its potential as an aggressiveness biomarker and providing paramount additional information influencing patient management.

18F-FDG PET/CT Versus 68Ga-PSMA-11 PET/CT in Evaluation of Distant Metastatic Disease in Recurrent Renal Cell Carcinoma

Prostate-specific membrane antigen (PSMA) expression has been observed in the neovasculature of various malignancies. We present a case of metastatic renal cell carcinoma (RCC) with comparative 18F-FDG PET/CT and 68Ga-PSMA-11 imaging in which FDG PET/CT failed to detect metastatic thyroid disease and showed less 18F-FDG-concentrating lesions at other sites, whereas 68Ga-PSMA-11 PET/CT identified metastatic thyroid disease and demonstrated intensely 68Ga-PSMA-11-expressing distant metastatic lesions. 68Ga-PSMA-11 PET/CT may be considered a potentially useful imaging technique in RCC to detect metastasis and to guide the choice of specific treatments, such as PSMA-based radionuclide therapy in patients with recurrent metastatic RCC.

Fluorescent Conjugates Based on Prostate-Specific Membrane Antigen Ligands as an Effective Visualization Tool for Prostate Cancer

Fluorescent dyes are widely used in histological studies and in intraoperative imaging, including surgical treatment of prostate cancer (PC), which is one of the most common types of cancerous tumors among men today. Targeted delivery of fluorescent conjugates greatly improves diagnostic efficiency and allows for timely correct diagnosis. In the case of PC, the protein marker is a prostate-specific membrane antigen (PSMA). To date, a large number of diagnostic conjugates targeting PSMA have been created based on modified urea. The review focuses on the conjugates selectively binding to PSMA and answers the following questions: What fluorescent dyes are already in use in the field of PC diagnosis? What factors influence the structure-activity ratio of the final molecule? What features should be considered when selecting a fluorescent tag to create new diagnostic conjugates? And what could be suggested to further development in this field at the present time?

Rapid Tumor Washout of 177Lu-PSMA Radioligand in Renal Cell Carcinoma

ABSTRACT

The role of prostate-specific membrane antigen (PSMA) targeted molecular imaging and radionuclide therapy in prostate cancer is well known. PSMA is also overexpressed in the neovasculature of a number of solid tumors, including renal cell carcinoma (RCC). Several studies have demonstrated the diagnostic utility of PSMA PET imaging in the setting of RCC. To date, no PSMA radioligand therapy of RCC patient has been reported according to literature. Here, we report our experience treating a patient with metastatic RCC with 177Lu-PSMA I&T radioligand therapy, but unexpected imaging findings with rapid washout of 177Lu-PSMA from the tumor.

Next generation radiotheranostics promoting precision medicine

Radiotheranostics is a field of rapid growth with some approved treatments including 131I for thyroid cancer, 223Ra for osseous metastases, 177Lu-DOTATATE for neuroendocrine tumors, and 177Lu-PSMA (prostate-specific membrane antigen) for prostate cancer, and several more under investigation. In this review, we will cover the fundamentals of radiotheranostics, the key clinical studies that have led to current success, future developments with new targets, radionuclides and platforms, challenges with logistics and reimbursement and, lastly, forthcoming considerations regarding dosimetry, identifying the right line of therapy, artificial intelligence and more.

Feasibility of biology-guided radiotherapy for metastatic renal cell carcinoma driven by PSMA PET imaging

Background

Biology-guided radiotherapy (BgRT) is a novel treatment where the detection of positron emission originating from a volume called the biological tracking zone (BTZ) initiates dose delivery. Prostate-specific membrane antigen (PSMA) positron emission tomography (PET) is a novel imaging technique that may improve patient selection for metastasis-directed therapy in renal cell carcinoma (RCC). This study aims to determine the feasibility of BgRT treatment for RCC.

Material and methods

All consecutive patients that underwent PSMA PET/CT scan for RCC staging at our institution between 2014 and 2020 were retrospectively considered for inclusion. GTVs were contoured on the CT component of the PET/CT scan. The tumor-to-background ratio was quantified from the normalized standardized uptake value (nSUV), defined as the ratio between SUVmax inside the GTV and SUVmean inside the margin expansion. Tumors were classified suitable for BgRT if (1) nSUV was greater or equal to an nSUV threshold and (2) if the BTZ was free of any PET-avid region other than the tumor.

Results

Out of this cohort of 83 patients, 47 had metastatic RCC and were included in this study. In total, 136 tumors were delineated, 1 to 22 tumors per patient, mostly in lung (40%). Using a margin expansion of 5 mm/10 mm/20 mm and nSUV threshold = 3, 66%/63%/41% of tumors were suitable for BgRT treatment. Uptake originating from another tumor, the kidney, or the liver was typically inside the BTZ in tumors judged unsuitable for BgRT.

Conclusions

More than 60% of tumors were found to be suitable for BgRT in this cohort of patients with RCC. However, the proximity of PET-avid organs such as the liver or the kidney may affect BgRT delivery.

Head-to-head comparison of [68Ga]Ga-P16-093 and 2-[18F]FDG PET/CT in patients with clear cell renal cell carcinoma: a pilot study

PURPOSE

This pilot study was prospectively designed to evaluate and compare the diagnostic value of PET/CT using a PSMA-specific tracer [⁶⁸Ga]Ga-P16-093 and a glucose metabolism probe 2-[¹⁸F]FDG in clear cell renal cell carcinoma (ccRCC) patients.

METHODS

Forty-two pathologically confirmed ccRCC patients were included. Within 1 week, each patient underwent [⁶⁸Ga]Ga-P16-093 and 2-[¹⁸F]FDG PET/CT. In addition to visual analysis of tumor number, the standardized uptake value (SUV) was measured for semiquantitative comparison and correlation analysis.

RESULTS

For primary ccRCC patients, [⁶⁸Ga]Ga-P16-093 PET/CT demonstrated a significantly higher detection rate (19/22 vs. 13/22, P = 0.031) and higher tumor uptake (15.7 ± 9.0 vs. 5.1 ± 3.4, P < 0.001) than 2-[¹⁸F]FDG PET/CT. In addition, the SUVmax of the primary tumor on [⁶⁸Ga]Ga-P16-093 and 2-[¹⁸F]FDG PET/CT was significantly correlated with pT stage (for [⁶⁸Ga]Ga-P16-093, r = 0.550, P = 0.008; for 2-[¹⁸F]FDG, r = 0.514, P = 0.014) and WHO/ISUP grade (for [⁶⁸Ga]Ga-P16-093, r = 0.566, P = 0.006; for 2-[¹⁸F]FDG, r = 0.492, P = 0.020), respectively. For metastatic ccRCC patients, [⁶⁸Ga]Ga-P16-093 PET/CT also demonstrated a better detection rate (21/22 vs. 14/22, P = 0.008) and higher tumor uptake (11.0 ± 6.4 vs. 4.4 ± 2.7, P < 0.001) than 2-[¹⁸F]FDG PET/CT. The SUVmax on [⁶⁸Ga]Ga-P16-093 PET/CT had a significant association with PSMA expression in primary ccRCC (r = 0.776, P < 0.001) and metastatic ccRCC (r = 0.626, P = 0.029).

CONCLUSIONS

[⁶⁸Ga]Ga-P16-093 PET/CT demonstrates significantly better tumor detectability than 2-[¹⁸F]FDG PET/CT for ccRCC patients.

TRIAL REGISTRATION

⁶⁸Ga-P16-093 and ¹⁸F-FDG PET/CT Imaging in the Same Group of Clear Cell Renal Cell Carcinoma Patients (NCT05432947, Registered 27 June 2021, retrospectively registered) URL OF REGISTRY: https://clinicaltrials.gov/ct2/show/NCT05432947 .

Exploration of 68Ga-labelled prostate-specific membrane antigen-11 PET/CT parameters for identifying PBRM1 status in primary clear cell renal cell carcinoma

AIM

To investigate the predictive value of ⁶⁸Ga-labelled prostate-specific membrane antigen-11 (⁶⁸Ga-PSMA-11) integrated positron-emission tomography (PET)/computed tomography (CT) in PBRM1-deficient clear cell renal cell carcinoma (ccRCC).

MATERIALS AND METHODS

A total of 41 patients with ccRCC, were enrolled retrospectively and underwent ⁶⁸Ga-PSMA-11 PET/CT preoperatively. Radiological parameters, including CT attenuation value and maximum standard uptake value (SUVmax), were derived. Immunohistochemical and multiple immunofluorescences staining were performed to evaluate the PBRM1 status and immune response. The predictive value of imaging factors was analysed using a receiver operator characteristic curve analysis. Univariate and multivariate logistic regression analyses were used to investigate the relationship between clinical and radiological variables and PBRM1 status.

RESULTS

A total of 41 patients were included in this study, with 14 patients having PBRM1-deficient status. The tumour diameter on imaging and SUVmax differed significantly in patients with different PBRM1 expression statuses and no difference in CT attenuation was identified. Univariate and multivariate logistic regression analyses showed SUVmax was an obvious predictor for identification of PBRM1-deficient tumours. In addition, PBRM1-deficient tumours tended to be accompanied by greater cytotoxic T-cell infiltration, although most of them were in an exhausted state.

CONCLUSIONS

⁶⁸Ga-PSMA-11 PET/CT could be used to discriminate invasive PBRM1-deficient ccRCC.

The Emerging Role of PET/CT with PSMA-Targeting Radiopharmaceuticals in Clear Cell Renal Cancer: An Updated Systematic Review

BACKGROUND

Recent articles proposed the employment of positron emission tomography/computed tomography (PET/CT) with prostate-specific membrane antigen (PSMA)-targeting radiopharmaceuticals in clear cell renal cell carcinoma (ccRCC).

METHODS

The authors performed a comprehensive literature search of studies on the performance of PET/CT with PSMA-targeting radiopharmaceuticals in ccRCC. Original articles concerning this imaging examination were included in newly diagnosed ccRCC patients and ccRCC patients with disease recurrence.

RESULTS

A total of sixteen papers concerning the diagnostic performance of PSMA-targeted PET/CT in ccRCC (331 patients) were included in this systematic review. The included articles demonstrated an excellent detection rate of PSMA-targeting PET/CT in ccRCC.

CONCLUSIONS

PSMA-targeted PET/CT seems promising in detecting ccRCC lesions as well as in discriminating the presence of aggressive phenotypes. Prospective multicentric studies are warranted to strengthen the role of PSMA-targeting PET/CT in ccRCC.

Special issue "The advance of solid tumor research in China": 68Ga-PSMA-11 PET/CT for evaluating primary and metastatic lesions in different histological subtypes of renal cell carcinoma

Conventional imaging examinations are not sensitive enough for the early detection of recurrent or metastatic lesions in renal cell carcinoma (RCC) patients. We aimed to explore the role of ⁶⁸ Ga-prostate specific membrane antigen (PSMA)-11 positron emission tomography (PET)/computed tomography (CT) in the detection of primary and metastatic lesions in such patients. We retrospectively analyzed 50 RCC patients who underwent ⁶⁸ Ga-PSMA-11 PET/CT from November 2017 to December 2020. We observed a higher median accuracy and tumor-to-background maximum standard uptake value (SUV_max ) ratio (TBR) of ⁶⁸ Ga-PSMA-11 PET/CT in clear cell RCC (ccRCC; 96.57% and 6.00, respectively) than in non-clear cell RCC (ncRCC; 82.05% and 2.99, respectively). The accuracies in detecting lesions in the renal region, bone, lymph nodes and lungs in ccRCC were 100.00%, 95.00%, 98.08% and 75.00%, respectively, and those in the renal region, bone and lymph nodes in ncRCC were 100.00%, 86.67% and 36.36%, respectively. The median TBRs of the lesions from the above locations were 0.38, 10.96, 6.69 and 13.71, respectively, in ccRCC and 0.13, 4.02 and 0.73, respectively, in ncRCC. The PSMA score evaluated with immunohistochemistry was correlated with the SUV_max (P = .046) in RCC. Higher PSMA scores were observed in ccRCC than in ncRCC (P = .031). ⁶⁸ Ga-PSMA-11 PET/CT resulted in changes in clinical management in 12.9% (4/31) of cases because of the discovery of new metastases not detected with conventional imaging. These results indicate that ⁶⁸ Ga-PSMA-11 PET/CT is a promising method for the detection of metastatic lesions in ccRCC, especially for those in the bone and lymph nodes.

Impact of Prostate-specific Membrane Antigen Positron Emission Tomography/Computed Tomography in the Management of Oligometastatic Renal Cell Carcinoma

Background

Prostate-specific membrane antigen (PSMA) is overexpressed in the neovasculature of renal cell carcinoma (RCC). However, there remains limited evidence regarding the use of PSMA positron emission tomography/computed tomography (PET/CT) in RCC.

Objective

To assess the impact of PSMA PET/CT in the management of metastatic RCC.

Design, setting, and participants

This was a retrospective review of patients who underwent PSMA PET/CT from 2014 to 2020 for restaging or suspected metastatic RCC in a tertiary academic setting.

Outcome measurements and statistical analysis

Management plans before and after PSMA PET/CT were recorded. Impact was classified as high (change of treatment intent, modality, or site), medium (change in treatment method), or low. Secondary outcomes included the patient-level detection rate, PSMA PET/CT parameters, sensitivity, and comparison to CT and, if available, fluorodeoxyglucose (FDG) PET/CT.

Results and limitations

Sixty-one patients met the inclusion criteria, of whom 54 (89%) had clear cell RCC. PSMA-positive disease was detected in 51 patients (84%). For 30 patients (49%) there was a change in management due to PSMA PET/CT (high impact, 29 patients, 48%). In 15 patients (25%), more metastases were detected on PSMA PET/CT than on CT. The sensitivity of combined PSMA PET/CT and diagnostic CT was 91% (95% confidence interval 77–98%). In a subcohort of 40 patients, the detection rate was 88% for PSMA and 75% for FDG PET/CT (p = 0.17). The maximum standardised uptake value (SUV_max) was higher for PSMA than for FDG PET/CT (15.2 vs 8.0; p = 0.02). Limitations include selection bias due to the retrospective design, and a lack of corresponding histopathology for all patients.

Conclusions

PSMA PET/CT is a promising imaging modality in metastatic RCC and led to a change in management in 49% of patients. PSMA PET/CT detected additional metastases compared to CT in 25% of patients and registered a significantly higher SUV_max than FDG PET/CT. Prospective studies are required to further define its role.

Patient summary

We report on a group of patients undergoing a new type of imaging for suspected advanced kidney cancer, called PSMA PET/CT. This imaging changed the management plan in 49% of the patients. PSMA PET/CT detected metastases in 84% of our patients and detected more metastases than computed tomography imaging in 25%.

Urothelial Carcinoma and Prostate-specific Membrane Antigen: Cellular, Imaging, and Prognostic Implications

CONTEXT

Staging, restaging, and surveillance of urothelial carcinoma (UC) is challenging due to suboptimal accuracy of standard of care imaging modalities. Prostate-specific membrane antigen (PSMA) imaging may serve to improve characterisation of UC.

OBJECTIVE

To appraise available literature regarding cellular, imaging, and prognostic implications of PSMA for UC.

EVIDENCE ACQUISITION

A systematic review was performed considering all available literature (including conference abstracts) published from 1990 to 2020 and reported according to Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines following registration in PROSPERO (CRD42020186744). All relevant texts relating to immunohistochemical analysis and PSMA-based imaging in UC were included and collated. Additionally, FOLH1 (gene encoding PSMA) expression according to The Cancer Genome Atlas (TCGA) database was analysed as well as according to consensus and TCGA molecular classification subtypes and subsequently compared with clinical outcomes.

EVIDENCE SYNTHESIS

PSMA expression across UC tumour tissue was heterogeneous (0-100%) but appeared to decrease with increased grade and stage. The TCGA analysis demonstrated loss of FOLH1 expression with increasing T stage (p = 0.0180) and N stage (p = 0.0269), and reduced FOLH1 expression was associated with worse disease-free survival. PSMA expression in UC neovasculature was variable but mostly increased (44-100%). Eleven reports of PSMA-based imaging for UC were identified, reporting on 18 patients. PSMA positron emission tomography (PET) imaging was positive in 17 out of 18 patients. The included literature review data were limited by mostly low-quality, retrospective studies.

CONCLUSIONS

Tissue PSMA, or FOLH1 expression, may inversely be associated with pathological and survival outcomes in localised UC. PSMA PET imaging may improve detection of metastatic disease and response to systemic therapy due to PSMA expression in neovasculature. Available evidence is limited; thus, larger, prospective studies are required to confirm early results and define populations that benefit most.

PATIENT SUMMARY

In this systematic review, we assess the potential role of prostate-specific membrane antigen in urothelial cancer. We found that its utility is in expression of blood vessels surrounding metastasis. We conclude that it may be beneficial in detecting metastasis and response to systemic therapies.

PSMA Radioligand Uptake as a Biomarker of Neoangiogenesis in Solid Tumours: Diagnostic or Theragnostic Factor?

Due to its overexpression on the surface of prostate cancer cells, prostate-specific membrane antigen (PSMA) is a relatively novel effective target for molecular imaging and radioligand therapy (RLT) in prostate cancer. Recent studies reported that PSMA is expressed in the neovasculature of various types of cancer and regulates tumour cell invasion as well as tumour angiogenesis. Several authors explored the role of diagnostic and therapeutic PSMA radioligands in various malignancies. In this narrative review, we describe the current status of the literature on PSMA radioligands' application in solid tumours other than prostate cancer to explore their potential role as diagnostic or therapeutic agents, with particular regard to the relevance of PSMA radioligand uptake as neoangiogenetic biomarker. Hence, a comprehensive review of the literature was performed to find relevant articles on the applications of PSMA radioligands in non-prostate solid tumours. Data on the general, methodological and clinical aspects of all included studies were collected. Forty full-text papers were selected for final review, 8 of which explored PSMA radioligand PET/CT performances in gliomas, 3 in salivary gland malignancies, 6 in thyroid cancer, 2 in breast cancer, 16 in renal cell carcinoma and 5 in hepatocellular carcinoma. In the included studies, PSMA radioligand PET showed promising performance in patients with non-prostate solid tumours. Further studies are needed to better define its potential role in oncological patients management, especially in those undergoing antineoangiogenic therapies, and to assess the efficacy of PSMA-RLT in this clinical context.

Recent advances in imaging techniques of renal masses

Multiphasic multidetector computed tomography (CT) forms the mainstay for the characterization of renal masses whereas magnetic resonance imaging (MRI) acts as a problem-solving tool in some cases. However, a few of the renal masses remain indeterminate even after evaluation by conventional imaging methods. To overcome the deficiency in current imaging techniques, advanced imaging methods have been devised and are being tested. This review will cover the role of contrast-enhanced ultrasonography, shear wave elastography, dual-energy CT, perfusion CT, MR perfusion, diffusion-weighted MRI, blood oxygen level-dependent MRI, MR spectroscopy, positron emission tomography (PET)/prostate-specific membrane antigen-PET in the characterization of renal masses.

Molecular Imaging of Renal Cell Carcinoma in Precision Medicine

Renal cell carcinoma (RCC) is the sixth most common cancer among men and the ninth among women, and its prognosis is closely correlated with metastasis. Targeted therapy and immunotherapy are the main adjuvant treatments for advanced RCC and require early diagnosis, precise assessment, and prediction of the therapeutic responses. Current conventional imaging methods of RCC only provide structural information rather than biological processes. Noninvasive diagnostic tools are therefore needed to image RCC early and accurately at the molecular level. Nuclear medicine imaging combines the high sensitivity of radionuclides with the high resolution of structural imaging to visualize the metabolic processes and specific targets of RCC for more accurate and reliable diagnosis, staging, prognosis prediction, and response assessment. This review summarizes the most recent applications of nuclear medicine receptor imaging and metabolic imaging in RCC and highlights future development perspectives in the field.

Imaging of Tumor-Associated Vascular Prostate-Specific Membrane Antigen in Woodchuck Model of Hepatocellular Carcinoma

BACKGROUND AND AIMS

Radiolabeled short peptide ligands targeting prostate-specific membrane antigen (PSMA) were developed initially for imaging and treatment of prostate cancers. While many nonprostate solid tumors including hepatocellular carcinoma (HCC) express little PSMA, their neovasculature expresses a high level of PSMA, which is avid for Gallium-68-labeled PSMA-targeting radio-ligand (⁶⁸Ga-PSMA-11) for positron emission tomography (PET). However, the lack of a spontaneous animal model of tumor-associated vascular PSMA overexpression has hindered the development and assessment of PSMA-targeting radioligands for imaging and therapy of the nonprostatic cancers. We identified detectable indigenous PSMA expression on tumor neovascular endothelia in a naturally occurring woodchuck model of HCC.

METHODS

Molecular docking was performed with 3 bait PSMA ligands and compared between human and woodchuck PSMA. Initially, PET images were acquired dynamically after intravenously injecting 37 MBq (1.0 mCi) of ⁶⁸Ga-PSMA-11 into woodchuck models of HCC. Subsequently, 10-minute static PET scans were conducted for other animals 1-hour after injection due to HCC and liver background uptake stabilization at 30-45 minutes after injection. Liver tissue samples were harvested after imaging, fresh-frozen for quantitative reverse transcription polymerase chain reaction and western blot for validation, or fixed for histology for correlation.

RESULTS

Our preclinical studies confirmed the initial clinical findings of ⁶⁸Ga-PSMA-11 uptake in HCC. The agents (ligands and antibodies) developed against human PSMA were found to be reactive against the woodchuck PSMA.

CONCLUSION

This animal model offers a unique opportunity for investigating the biogenesis of tumor-associated vascular PSMA, its functional role(s), and potentials for future treatment strategies targeting tumor vascular PSMA using already developed PSMA-targeting agents.

Preliminary Evaluation of 68Ga-P16-093, a PET Radiotracer Targeting Prostate-Specific Membrane Antigen in Prostate Cancer

PURPOSE

Prostate-specific membrane antigen (PSMA) is a promising molecular target for imaging of prostate adenocarcinoma. ⁶⁸Ga-P16-093, a small molecule PSMA ligand, previously showed equivalent diagnostic performance compared to ⁶⁸Ga-PSMA-11 PET/CT in a pilot study of prostate cancer patients with biochemical recurrence (BCR). We performed a pilot study for further characterization of ⁶⁸Ga-P16-093 including comparison to conventional imaging.

PROCEDURES

Patients were enrolled into two cohorts. The biodistribution cohort included 8 treated prostate cancer patients without recurrence, who underwent 6 whole body PET/CT scans with urine sampling for dosimetry using OLINDA/EXM. The dynamic cohort included 15 patients with BCR and 2 patients with primary prostate cancer. Two patients with renal cell carcinoma were also enrolled for exploratory use. A dynamic PET/CT was followed by 2 whole body scans for imaging protocol optimization based on bootstrapped replicates. ⁶⁸Ga-P16-093 PET/CT was compared for diagnostic performance against available ¹⁸F-fluciclovine PET/CT, ^99mTc-MDP scintigraphy, diagnostic CT, and MRI.

RESULTS

⁶⁸Ga-P16-093 deposited similar effective dose (0.024 mSv/MBq) and lower urinary bladder dose (0.064 mSv/MBq) compared to ⁶⁸Ga-PSMA-11. The kidneys were the critical organ (0.290 mSv/MBq). While higher injected activities were preferable, lower injected activities at 74-111 MBq (2-3 mCi) yielded 80% retention in signal-to-noise ratio. The optimal injection-to-scan interval was 60 min, with acceptable delay up to 90 min. ⁶⁸Ga-P16-093 PET/CT showed superior diagnostic performance over conventional imaging with overall patient-level lesion detection rate of 71%, leading to a change in management in 42% of the patients.

CONCLUSIONS

Based on its favorable imaging characteristics and diagnostic performance in prostate cancer, ⁶⁸Ga-P16-093 PET/CT merits further investigation in larger clinical studies.

PSMA PET/CT in Renal Cell Carcinoma: An Overview of Current Literature

Although the vast majority of prostate-specific membrane antigen (PSMA) positron emission tomography (PET) imaging occurs in the field of prostate cancer, PSMA is also highly expressed on the cell surface of the microvasculature of several other solid tumors, including renal cell carcinoma (RCC). This makes it a potentially interesting imaging target for the staging and monitoring of RCC. The objective of this review is to provide an overview of the current evidence regarding the use of PSMA PET/Computed Tomography in RCC patients.

Socio-economic burden of disease: Survivorship costs for renal cell carcinoma

OBJECTIVE

The objective of this study is to assess the risk-stratified 10-year socio-economic burden of renal cell carcinoma (RCC) follow-up costs after initial treatment in Germany from 2000 to 2020.

METHODS

A micro-costing method considering direct and indirect medical expenditure associated with follow-up procedures was employed to calculate survivorship costs per patient. The frequencies of physician-patient visits, examinations and diagnostic tests were extracted from guidelines, whilst expenses were sourced from literature and official scales of tariffs. Societal costs were calculated based on three perspectives: patients, providers and insurers.

RESULTS

Mean societal 10-year follow-up costs per patient amounted to EUR 3,377 (95%CI: 2,969-3,791) for low-risk, EUR 3,367 (95%CI: 3,003-3,692) for medium-risk and EUR 4,299 (95%CI: 3,807-4,755) for high-risk RCC in 2020. Spending increased by +32% from 2000 to 2020 for low-risk RCC, whilst medium-and high-risk RCC expenditure was cut by -39% and -22%, respectively. Patients shouldered 27%, providers 43% and insurers 35% of costs in 2020. Resources were consumed by medical imaging (52%), physician-patient consultations (31%), travel expenses (17%) and blood tests (1%).

CONCLUSION

Results highlight the economic burden cancer survivorship poses for society. Cancer survivors require individualised, evidence-based and insurance-covered follow-up schedules to permit the early detection of side-effects, metastasis and secondary malignancies.

De Quervain Subacute Thyroiditis With Moderate PSMA Uptake Mimicking Thyroid Metastasis of Renal Cell Carcinoma

ABSTRACT

PSMA-targeted PET/CT can be used for diagnosis and staging of clear cell renal cell carcinoma. A 68-year-old woman with suspected hepatic metastases from clear cell renal cell carcinoma underwent PET/CT with 68Ga-PSMA, which showed a focus of moderately increased tracer uptake in the right thyroid lobe. Sonography displayed a correlating hypoechogenic, ill-defined node (TIRADS 5). Right hemithyroidectomy was performed in the assumption of a solitary metastasis of renal cell carcinoma. Histologic examination revealed subacute granulomatous thyroiditis (De Quervain thyroiditis) without evidence of malignancy.

Role of PSMA-ligands imaging in Renal Cell Carcinoma management: current status and future perspectives

Background

Renal masses detection is continually increasing worldwide, with Renal Cell Carcinoma (RCC) accounting for approximately 90% of all renal cancers and remaining one of the most aggressive urological malignancies. Despite improvements in cancer management, accurate diagnosis and treatment strategy of RCC by computed tomography (CT) and magnetic resonance imaging (MRI) are still challenging. Prostate-Specific Membrane Antigen (PSMA) is known to be highly expressed on the endothelial cells of the neovasculature of several solid tumors other than prostate cancer, including RCC. In this context, recent preliminary studies reported a promising role for positron emission tomography (PET)/CT with radiolabeled molecules targeting PSMA, in alternative to fluorodeoxyglucose (FDG) in RCC patients.

Purpose

The aim of our review is to provide an updated overview of current evidences and major limitations regarding the use of PSMA PET/CT in RCC.

Methods

A literature search, up to 31 December 2021, was performed using the following electronic databases: PubMed, SCOPUS, Web of Science, and Google Scholar.

Results

The findings of this review suggest that PSMA PET/CT could represent a valid imaging option for diagnosis, staging, and therapy response evaluation in RCC, particularly in clear cell RCC.

Conclusions

Further studies are needed for this “relatively” new imaging modality to consolidate its indications, timing, and practical procedures.

Determination of optimal 68 Ga-PSMA PET/CT imaging time in prostate cancers by total-body dynamic PET/CT

BACKGROUND

⁶⁸ Ga-PSMA PET/CT has been widely used in patients with prostate cancer. Due to the limited axial field of view of conventional PET scanners, whole-body dynamic ⁶⁸ Ga-PSMA PET/CT has not been performed. We investigated the time-activity curves (TACs) of prostate cancer pathological lesions and physiologic bladder activity to determine the optimal ⁶⁸ Ga-PSMA PET/CT imaging time by total-body (TB) PET/CT.

METHODS

Dynamic TB-PET performed on 11 patients with prostate cancer was analyzed. TACs were obtained by drawing regions of interest in normal organs and pathological lesions (primary prostate lesions and lymph nodes and bone metastases). We evaluated the ⁶⁸ Ga-PSMA uptake pattern of normal organs, urinary bladder, and pathological lesions.

RESULTS

The urinary bladder TAC increased slowly between 180 and 330 s post-injection and then rapidly between 5.5 and 60.0 min post-injection. The pathological lesion uptake increased rapidly during the first 5 min post-injection and then slowly through the remaining 55 min. Six minutes post-injection was the optimal time with the highest pathological lesion SUV_mean values still higher than the urinary bladder activity value. However, these prostate lesion, lymph node metastasis, and bone metastasis SUV_mean values were one-third, one-half, and one-half the corresponding values 60 min post-injection, suggesting that early imaging might miss low PSMA uptake lesions. A minimum of 35 min post-injection was required for the pathological lesions to have SUV_mean values similar to the corresponding values at 60 min post-injection (all P > 0.05), even though the pathological lesion SUV_mean values showed a continuous upward trend through the 60 min.

CONCLUSIONS

Combining early dynamic ⁶⁸ Ga-PSMA PET (75-360 s) and conventional static imaging 60 min post-injection could avoid the urinary bladder activity interference to better detect pathological lesions and lesions with relatively low PSMA uptake. The pathological lesion SUV_mean values at 35-59 min and 60 min post-injection were similar, so ⁶⁸ Ga-PSMA PET imaging could also be made at 35-59 min post-injection.

Case Report: Early 68Ga-PSMA-PET Metabolic Assessment and Response to Systemic Treatment for First-Line Metastatic Clear Cell Renal Cell Carcinoma; About Two Clinical Cases

Early evaluation of response to anticancer treatment in metastatic renal cell carcinoma (RCC) is challenging as responses are sometimes delayed, as mixed responses can occur, and as conventional imaging have some limitations. As PSMA has been previously identified in neovasculature of clear cell RCC (ccRCC), ⁶⁸Ga-PSMA-Positron Emitted Tomography (PET) could appear as an interesting tool to evaluate therapeutic response. We describe the association of an early decrease in ⁶⁸Ga metabolism (at 8 weeks after treatment onset) and further radiological response (at 12 weeks after treatment onset) to treatment in two patients with different sensitivity to axitinib–pembrolizumab combination. Interestingly, one of these patients presented an initial progressive disease on pembrolizumab alone and a subsequent response to axitinib alone in the disease course; these response profiles were associated with absence of decrease and subsequent decrease in the ⁶⁸Ga metabolism, respectively. Even if further prospective trials are needed, ⁶⁸Ga-PSMA-PET may appear as a promising way for early prediction of response to ccRCC systemic treatment.

The role of dual tracer PSMA and FDG PET/CT in renal cell carcinoma (RCC) compared to conventional imaging: A multi-institutional case series with intra-individual comparison

PURPOSE

The objective of this study was to perform an intra-individual dual tracer comparison of Fluorodeoxyglucose (FDG) and Prostate Specific Membrane Antigen (PSMA) computed tomography (CT)/Positron Emission Tomography (PET) against standard of care (SOC) imaging for the characterisation, staging and restaging of renal cell carcinoma (RCC).

METHODS

A multicentre retrospective cohort study was performed at 3 major tertiary referral institutions in Brisbane, Australia between 2015 and 2020. All patients who underwent both PSMA and FDG PET/CT following SOC imaging for investigation of RCC were identified. Clinical details, imaging characteristics and histopathology were collected prior to univariate statistical analysis.

RESULTS

Eleven patients who underwent dual tracer PET/CT were included. Mean age was 65.5 years (SD 8.8). Most patients were male (64%) with clear cell morphology (91%). The indication for dual tracer PET was staging (36%) and restaging after radical/partial nephrectomy (64%). Primary tumour assessment showed mixed avidity patterns (concordant 40%, discordant favouring PSMA 20%, and FDG 40%). Metastatic disease assessment showed concordant avidity in 6 patients (55%), concordant negative in 3 (27%), and discordant uptake favouring PSMA. PET outperformed SOC imaging for assessment of metastatic disease in 5 patients (45%) and equivalent for the remainder. A change in management was noted in three cases (27%).

CONCLUSION

Dual tracer FDG and PSMA PET/CT for assessment of primary and metastatic RCC were mostly concordant. PET imaging outperformed conventional imaging and led to a change in management for 1 in 4 patients. Further studies with larger samples sizes are required to validate these findings and identify characteristics to guide patient selection for selective or dual tracer use.

18F-DCFPyL PET/CT in Metastatic Renal Cell Carcinoma

Targeted molecular imaging with positron emission tomography (PET) utilize chemical ligands is a peptide that specifically targets a receptor of interest. Prostate specific membrane antigen (PSMA) is substantially upregulated in prostate cancer but is also expressed in the neovascular tissue of several malignancies, including renal cell carcinoma (RCC). Radiolabeled peptide targets for PSMA may be helpful in detecting metastatic RCC lesions. This teaching case provides an insight incidental detection of RCC metastatic disease with PSMA targeted PET and explores potential in deliberate evaluation of RCC with PSMA targeted tracers.

68Ga-PSMA PET/CT to Distinguish Brain Metastasis of Renal Cell Carcinoma From Radiation Necrosis After Stereotactic Radiosurgery

ABSTRACT

Renal cell carcinoma (RCC) is the most common primary malignancy of the kidney. Approximately 35% of patients of RCC presents with distant metastasis at initial evaluation. CT and MRI are the mainstay imaging modalities. Distinguishing radiation necrosis from tumor progression after stereotactic radiosurgery is challenging. Herein, we present a case of a 43-year-old man with RCC who was treated with stereotactic radiosurgery for brain metastases. We want to emphasize the potential value of 68Ga-PSMA PET/CT imaging in the differential diagnosis and follow-up of tumor progression from radiation necrosis in RCC patients.

Antibodies targeting Prostate-Specific Membrane Antigen positive prostate cancer: from diagnostic imaging to theranostics

PURPOSE OF REVIEW

Targeting Prostate-Specific Membrane Antigen (PSMA) has paved the way for personalized medicine in prostate cancer (PCa) patients. This review aims to highlight the role of PSMA targeting antibodies in PCa, for diagnostic and therapeutic purposes.

RECENT FINDINGS

PSMA Positron Emission Tomography/Computed Tomography has been a game changer in the diagnosis of PCa in the recent decade. Two anti-PSMA monoclonal antibodies have been studied in PCa: 7E11-C35 (limited use) and J591. J591 antibody was used for diagnostic purposes coupled with different radionuclides. Most importantly, it was combined to numerous therapeutic radionuclides such as Lutetium-177 (177Lu), Yttrium-90 (90Y), Indium-111 (111In), and Actinium-225 (225Ac). It was also conjugated to drugs forming antibody-drug conjugates (e.g. MLN2704 and PSMA-ADC). These compounds were tested in recent phase I/II clinical trials.

SUMMARY

PSMA targeting antibodies are very promising for further clinical investigation and continue to be a momentous research area, for both imaging and therapeutic settings. Although some clinical trials resulted in unfavorably safety profiles for some antibodies, they validated PSMA as a crucial immunoconjugate target.

Utility of 18F-Prostate-Specific Membrane Antigen 1007 in Imaging of Tumor Thrombus of Renal Cell Carcinoma

ABSTRACT

A 64-year-old man was referred for 18F-prostate-specific membrane antigen 1007 PET/CT with a suspicion of recurrence and metastases of renal cell carcinoma after the resection of right renal cell carcinoma. The scan showed intense tracer concentration in the inferior vena cava and the right atrium, which was later proven on histopathologic examination as tumor thrombus of renal cell carcinoma. Adding on to previous studies with 18F-prostate-specific membrane antigen 1007 in the primary renal tumor, the case proved that the tumor thrombus of renal cell carcinoma could also show intense tracer concentration and further highlights its utility in renal cell carcinoma.

Complementary Role of 68Ga-Prostate-Specific Membrane Antigen and 18F-FDG PET/CT for Evaluation of Metastases and Treatment Response in Renal Cell Carcinoma

ABSTRACT

We present a case of clear cell renal cell carcinoma, which demonstrates complementary FDG and prostate-specific membrane antigen (PSMA) uptake on metastases in PET/CT, as an example of tumor heterogeneity. The patient had non-FDG-avid lung and bone metastases with PSMA uptake, whereas metastatic cervical and axillary lymph nodes showed vice versa, and skeletal muscle metastasis to vastus lateralis, which is an unusual region for metastasis, showed both PSMA and FDG positivity. In response assessment, mix response was detected. It seems that 68Ga-PSMA and 18F-FDG may have a complementary role in demonstration of metastasis accurately and assessment of treatment response in clear cell renal cell carcinoma.

PSMA-PET/CT in Patients with Recurrent Clear Cell Renal Cell Carcinoma: Histopathological Correlations of Imaging Findings

PET/CT with prostate-specific membrane antigen (PSMA)-targeted tracers has been used in the diagnosis and staging of patients with clear cell renal cell carcinoma (ccRCC). For ccRCC primary tumors, PET parameters were shown to predict histologic grade and features. The aim of this study was to correlate PSMA PET/CT with histopathological findings in patients with metastatic recurrence of ccRCC. Patients with ccRCC who underwent PSMA-targeted PET/CT and subsequent histopathological evaluation of suspicious lesions were included. Specimens underwent immunohistochemical marking. Lesion diameter, volume and tracer uptake were correlated with the extent and intensity of molecular PSMA expression and with clinical findings. Twelve PET-positive lesions of nine patients were evaluated. Eleven ccRCC metastases and one prostate carcinoma were detected histopathologically. Molecular PSMA expression was detected in all lesions, which intensity and distribution did not correlate with PET parameters. PSMA-targeted PET/CT is a feasible tool for the evaluation of patients with ccRCC but cannot reliably predict histologic features of metastases. PSMA may also be expressed in malignant lesions other than ccRCC, leading to incidental detection of these tumors.

PSMA radioligand therapy for solid tumors other than prostate cancer: background, opportunities, challenges, and first clinical reports

In the past decade, a growing body of literature has reported promising results for prostate-specific membrane antigen (PSMA)-targeted radionuclide imaging and therapy in prostate cancer. First clinical studies evaluating the efficacy of [¹⁷⁷Lu]Lu-PSMA radioligand therapy (PSMA-RLT) demonstrated favorable results in prostate cancer patients. [¹⁷⁷Lu]Lu-PSMA is generally well tolerated due to its limited side effects. While PSMA is highly overexpressed in prostate cancer cells, varying degrees of PSMA expression have been reported in other malignancies as well, particularly in the tumor-associated neovasculature. Hence, it is anticipated that PSMA-RLT could be explored for other solid cancers. Here, we describe the current knowledge of PSMA expression in other solid cancers and define a perspective towards broader clinical implementation of PSMA-RLT. This review focuses specifically on salivary gland cancer, glioblastoma, thyroid cancer, renal cell carcinoma, hepatocellular carcinoma, lung cancer, and breast cancer. An overview of the (pre)clinical data on PSMA immunohistochemistry and PSMA PET/CT imaging is provided and summarized. Furthermore, the first clinical reports of non-prostate cancer patients treated with PSMA-RLT are described.

Automatic radiosynthesis and preclinical evaluation of 18F-AlF-PSMA-NF as a potential PET probe for prostate cancer imaging

Facile automatic production is important for the application of prostate-specific membrane antigen (PSMA) tracers in clinical practice. We developed a new ¹⁸F-AlF-labelled PSMA probe-¹⁸F-AlF-PSMA-NF-and explore its automated production method and potential value in clinical settings. ¹⁸F-AlF-PSMA-NF was prepared using an automated method with dimethylformamide (DMF) as the solvent in a positron emission tomography (PET)-MF-2 V-IT-I synthesizer. Tracer characteristics were examined both in vitro and in vivo. Micro-PET/computed tomography (CT) was performed to investigate the utility of ¹⁸F-AlF-PSMA-NF for imaging PSMA-positive tumours in vivo. ¹⁸F-AlF-PSMA-NF was prepared automatically within 35 min with a non-attenuation correction yield of 37.9 ± 11.2%. The tracer was hydrophilic, had a high affinity for PSMA (Kd = 2.58 ± 0.81 nM), and showed stability in both in vitro and in vivo conditions. In the cellular experiments, ¹⁸F-AlF-PSMA-NF uptake in PSMA-positive LNCaP cells was significantly higher than that in PSMA-negative PC-3 cells (P < 0.001), and could be blocked by excess ZJ-43-a PSMA inhibitor (P < 0.001). LNCaP tumours were clearly visualized by ¹⁸F-AlF-PSMA-NF on micro-PET/CT, with a high level of uptake (13.72 ± 2.01 percent injected dose per gram of tissue [%ID/g]) and high tumour/muscle ratio (close to 50:1). The PSMA-positive LNCaP tumours had a significantly higher uptake than PSMA-negative PC-3 tumours (13.72 ± 2.01%ID/g vs. 1.07 ± 0.48%ID/g, t = 10.382, P < 0.001), and could be blocked by ZJ-43 (13.72 ± 2.01%ID/g vs. 2.77 ± 1.44%ID/g, t = 8.14, P < 0.001). A new ¹⁸F-AlF-labelled PSMA probe-¹⁸F-AlF-PSMA-NF-was successfully developed and can be prepared automatically. It has the biological characteristics resembling that of a PSMA-based probe and can potentially be used in clinical settings.

Current and future perspectives on functional molecular imaging in nephro-urology: theranostics on the horizon

In recent years, a paradigm shift from single-photon-emitting radionuclide radiotracers toward positron-emission tomography (PET) radiotracers has occurred in nuclear oncology. Although PET-based molecular imaging of the kidneys is still in its infancy, such a trend has emerged in the field of functional renal radionuclide imaging. Potentially allowing for precise and thorough evaluation of renal radiotracer urodynamics, PET radionuclide imaging has numerous advantages including precise anatomical co-registration with CT images and dynamic three-dimensional imaging capability. In addition, relative to scintigraphic approaches, PET can allow for significantly reduced scan time enabling high-throughput in a busy PET practice and further reduces radiation exposure, which may have a clinical impact in pediatric populations. In recent years, multiple renal PET radiotracers labeled with 11C, 68Ga, and 18F have been utilized in clinical studies. Beyond providing a precise non-invasive read-out of renal function, such radiotracers may also be used to assess renal inflammation. This manuscript will provide an overview of renal molecular PET imaging and will highlight the transformation of conventional scintigraphy of the kidneys toward novel, high-resolution PET imaging for assessing renal function. In addition, future applications will be introduced, e.g. by transferring the concept of molecular image-guided diagnostics and therapy (theranostics) to the field of nephrology.