The roles of 68 Ga-PSMA PET/CT and 18 F-FDG PET/CT imaging in patients with triple-negative breast cancer and the association of tissue PSMA and claudin 1, 4, and 7 levels with PET findings

E-Urea-K-Based PSMA Imaging Served as an Alternative in Assessing Tumor Neovascularization via Targeting CD31

To reveal the natural correlation between prostate-specific membrane antigen (PSMA) imaging and tumor neovascularization in prostate cancer and further explore E-urea-K-based PSMA-targeted (EK-PSMA) imaging as a potential indicator of tumor neovascularization, the 22Rv1 mouse models were established and underwent 99mTc-HYNIC-ALUG SPECT/CT. Pearson correlation analysis was applied to assess the relationship between tumor tracer uptake and tumor characteristics, including size, glucose metabolism, and cell phenotypes (e.g., Ki-67, VEGF, CD31, and PSMA). Then, molecular docking further identified the key factors of EK-PSMA imaging, specifically related to tumor neovascularization. Finally, animal models with positive and negative PSMA expression (22Rv1, LNCaP, U87, SAOS-2, A549, and ACHN) were subjected to antibody-targeted blockade to verify the role of these key factors in EK-PSMA imaging. The Pearson's r values of tracer uptake correlated with CD31 and tumor size were 0.82 and 0.99, respectively (P < 0.05), and the correlations of tracer uptake with SUVmax, SUVmean, Ki-67, VEGF, and PSMA expressions were 0.47, 0.20, 0.69, -0.65, and 0.20, respectively (all P > 0.05). Molecular docking confirmed the affinity of E-urea-K to PSMA (two sites, binding scores, -5.4 kcal/mol and -6.0 kcal/mol) and CD31 (one site, binding score, -5.1 kcal/mol). The blockade of the CD31 antibody partially reduced the 99mTc-HYNIC-ALUG uptake in five other types of tumors (paired t test, P = 0.0478). The Pearson's r value of CD31 staining and tracer uptake prior to the antibody blockade was 0.84 (P < 0.05). Additionally, when removing the PSMA-positive models (22Rv1 and LNCaP), the Pearson's r value of CD31 staining and tracer uptake prior to the antibody blockade was 0.99 (P < 0.05). Thus, CD31 was found to be a mutual target of EK-PSMA imaging; therefore, EK-PSMA imaging provides a viable assessment option for tumor neovascularization, especially for PSMA-negative tumors.

The impact of PET imaging on triple negative breast cancer: an updated evidence-based perspective

INTRODUCTION

Triple-negative breast cancer (TNBC) is a subtype of breast cancer characterized by the absence of estrogen, progesterone, and HER2 receptors. It predominantly affects younger women and is associated with a poor prognosis. This systematic review aims to evaluate the current role of positron emission tomography (PET) in the management of TNBC patients and to identify future research directions.

METHODS

We systematically searched the PubMed, Scopus, and Web of Science databases up to February 2024. A team of five researchers conducted data extraction and analysis. The quality of the selected studies was assessed using a specific evaluation form.

RESULTS

Twenty-eight studies involving 2870 TNBC patients were included in the review. Key clinical applications of PET in TNBC included predicting pathological complete response (pCR) in patients undergoing neoadjuvant chemotherapy (NAC), assessing the prognostic value of baseline PET, and initial disease staging. Two studies utilized PSMA-ligand agents, while the majority used [18F]FDG-based PET. Significant associations were found between baseline [18F]FDG uptake and molecular biomarkers such as PDL-1, androgen receptor, and Ki67. Baseline [18F]FDG PET led to the upstaging of patients from stage IIB to stage IV, influencing treatment decisions and survival outcomes. In the NAC setting, serial PET scans measuring changes in [18F]FDG uptake, indicated by maximum standardized uptake value (SUVmax), predicted pCR with varying cut-off values correlated with different response rates. Semiquantitative parameters such as metabolic tumor volume (MTV) and PET lung index were prognostic for metastatic disease.

CONCLUSIONS

In TNBC patients, [18F]FDG PET is essential for initial disease staging in both localized and metastatic settings. It is also useful for assessing treatment response to NAC. The ability of PET to correlate metabolic activity with molecular markers and predict treatment outcomes highlights its potential in TNBC management. Further prospective studies are needed to refine these clinical indications and establish its definitive role.

Diagnostic Performance of Prostate-Specific Membrane Antigen-Targeted Positron Emission Tomography in Patients Diagnosed with Different Types of Breast Cancer: A Systematic Review

Recent research has proposed using positron emission tomography/computed tomography (PET/CT) along with the administration of prostate-specific membrane antigen (PSMA)-targeting radiopharmaceuticals to identify breast cancer (BC) lesions. An extensive literature review to investigate the possible diagnostic utility of PET/CT with PSMA-targeting radiopharmaceuticals in BC patients was performed. The research comprised different clinical scenarios, including both newly diagnosed BC patients and those who had experienced disease relapse. This updated systematic review encompassed six studies investigating the diagnostic efficacy of PSMA-targeted PET/CT in BC. Throughout all clinical settings investigated, the papers presented data demonstrating a modest diagnostic performance of PSMA-targeted PET/CT in different subtypes of BC. In this setting, PSMA-guided PET/CT showed slightly higher accuracy in patients diagnosed with triple-negative BC. Based on the current literature, PSMA-targeted PET/CT cannot be suggested as a diagnostic tool to assess BC extent in any clinical scenario. However, based on the PSMA expression observed in triple-negative patients, it can be proposed as a tool to evaluate whether BC patients could benefit from PSMA-targeting radioligand therapy.

Radiotracer Innovations in Breast Cancer Imaging: A Review of Recent Progress

This review focuses on the pivotal role of radiotracers in breast cancer imaging, emphasizing their importance in accurate detection, staging, and treatment monitoring. Radiotracers, labeled with radioactive isotopes, are integral to various nuclear imaging techniques, including positron emission tomography (PET) and positron emission mammography (PEM). The most widely used radiotracer in breast cancer imaging is 18F-fluorodeoxyglucose (18F-FDG), which highlights areas of increased glucose metabolism, a hallmark of many cancer cells. This allows for the identification of primary tumors and metastatic sites and the assessment of tumor response to therapy. In addition to 18F-FDG, this review will explore newer radiotracers targeting specific receptors, such as estrogen receptors or HER2, which offer more personalized imaging options. These tracers provide valuable insights into the molecular characteristics of tumors, aiding in tailored treatment strategies. By integrating radiotracers into breast cancer management, clinicians can enhance early disease detection, monitor therapeutic efficacy, and guide interventions, ultimately improving patient outcomes. Ongoing research aimed at developing more specific and sensitive tracers will also be highlighted, underscoring their potential to advance precision medicine in breast cancer care.

Prostate-Specific Membrane Antigen Positron Emission Tomography Oncological Applications beyond Prostate Cancer in Comparison to Other Radiopharmaceuticals

BACKGROUND

Prostate-specific membrane antigen (PSMA) is a type II transmembrane glycoprotein overexpressed on the surface of tumor cells in most of the patients affected by prostate adenocarcinoma (PCa). However, PSMA expression has also been demonstrated in the endothelial cells of newly formed vessels of various solid tumors, suggesting a role for PSMA in neoangiogenesis. In this scenario, gallium-68 (68Ga) or fluoro-18 (18F)-labeled PSMA positron emission tomography (PET) may play a role in tumors other than PCa, generally evaluated employing other radiopharmaceuticals targeting different pathways. This review aims to investigate the detection rate of PSMA-PET compared to other radiopharmaceuticals (especially [18F]FDG) in non-prostate tumors to identify patients who may benefit from the use of such a theragnostic agent.

METHODS

We performed a bibliographic search on three different databases until February 2024 using the following terms: "positron emission tomography", "PET", "PET/CT", "Prostate-specific membrane antigen", "PSMA", "non-prostate", "not prostate cancer", "solid tumor", "FDG", "Fluorodeoxyglucose", "FAPi", "FET", "MET", "DOPA", "choline", "FCH", "FES", "DOTATOC", "DOTANOC", and "DOTATATE". Only original articles edited in English with at least 10 patients were included.

RESULTS

Out of a total of 120 articles, only 25 original articles comparing PSMA with other radiotracers were included in this study. The main evidence was demonstrated in renal cell carcinoma, where PSMA showed a higher detection rate compared to [18F]FDG PET/CT, with implications for patient management. PSMA PET may also improve the assessment of other entities, such as gliomas, in defining regions of early neoangiogenesis. Further data are needed to evaluate the potential role of PSMA-PET in triple-negative breast cancer as a novel therapeutic vascular target. Finally, unclear applications of PSMA-PET include thyroid and gastrointestinal tumors.

CONCLUSIONS

The present review shows the potential use of PSMA-labeled PET/CT in solid tumors beyond PCa, underlining its value over other radiopharmaceuticals (mainly [18F]FDG). Prospective clinical trials with larger sample sizes are crucial to further investigate these possible clinical applications.

The clinical signification and application value of [68Ga]Ga-PSMA imaging in thyroid malignancy

PURPOSE

Approximately 5% of differentiated thyroid cancers lose the ability to uptake iodine, leading to limited treatment options and poor prognosis due to invasion and distant metastasis. PSMA imaging probes have been proposed as a potential diagnostic and therapeutic tool for iodine-refractory thyroid cancer. However, there are limited reports and significant heterogeneity in patient selection, warranting further exploration of the application value of PSMA in thyroid cancer.

METHODS

We performed Western Blot, PCR, and [68Ga]Ga-PSMA uptake experiments on cell lines and conducted in vivo small animal imaging. Clinical and radiological results of included differentiated thyroid cancer patients were collected. (Trial registration number: 2021-669, Trial registration date: December 30, 2021).

RESULTS

PSMA expression levels were significantly higher in poorly differentiated thyroid cancer (7.86 ± 1.90 vs. 1.00 ± 0, P < 0.01; 7.86 ± 1.90 vs. 0.03 ± 0.02, P < 0.01), but [68Ga]Ga-PSMA imaging correlated with tumor burden, such as 18F-FDG (8.08 ± 7.74 and 5.67 ± 4.23, P = 0.01) and Tg levels (307.1 ± 183.4 vs. 118.0 ± 116.1, P = 0.002).

CONCLUSION

Our results showed that PSMA expression increased with the decrease of thyroid cancer differentiation. However, the level of [68Ga]Ga-PSMA uptake in thyroid cancer patients was not significantly associated with the degree of thyroid cancer differentiation, but also with the metabolism and burden of tumors such as 2-[18F]FDG and Tg levels. These findings provide additional clinical significance and application value for PSMA in thyroid cancer.

Head-to-Head Comparison of [18F]PSMA-1007 and [18F]FDG PET/CT in Patients with Triple-Negative Breast Cancer

BACKGROUND

Triple-negative breast cancer (TNBC) exhibits high aggressiveness and a notably poorer prognosis at advanced stages. Nuclear medicine offers new possibilities, not only for diagnosis but also potentially promising therapeutic strategies. This prospective study explores the potential of prostate-specific membrane antigen (PSMA) as a diagnostic and therapeutic target in TNBC.

METHODS

the research investigates PSMA expression in vivo among TNBC patients using [18F]PSMA-1007 PET/CT and compares it head-to-head with the standard-of-care [18F]FDG PET/CT.

RESULTS

The study involves 10 TNBC patients, revealing comparable uptake of [18F]PSMA-1007 and [18F]FDG in primary and metastatic lesions. Nodal metastases were found in eight patients, showing similar SUVmax values in both modalities. Two patients had uncountable lung metastases positive in both [18F]FDG and [18F]PSMA-1007 scans. PET-positive bone metastases were identified by 18F-PSMA in four patients, while elevated [18F]FDG uptake was found only in three of them. Distant metastases displayed higher SUVmax values in the [18F]PSMA-1007 PET/CT, as compared to [18F]FDG. Additionally, brain metastases were exclusively detected using [18F]PSMA-1007.

CONCLUSIONS

the findings provide valuable insights into the expression of PSMA in TNBC and underscore the potential clinical significance of [18F]PSMA-1007 PET/CT in enhancing both diagnostic and therapeutic approaches for this aggressive breast cancer subtype.