Oncologic Staging with 68Ga-FAPI PET/CT Demonstrates a Lower Rate of Nonspecific Lymph Node Findings Than 18F-FDG PET/CT

Synthesis and biological evaluation of a 68Ga-labeled glucose derivative PET probe [68Ga]Ga-NOTA-SDG

PURPOSE

Currently, 2-[18F]fluoro-2-deoxy-D-glucose ([18F]FDG) has been widely used in clinical diagnostics for tumors. However, its application is hindered by several limitations, including low tumor specificity, the need for accelerator production of 18F, and complex synthesis procedures. In this study, a 68Ga-labeled glucose derivative PET molecular probe, [68Ga]Ga-NOTA-SDG, was designed to overcome these issues with the advantages of 68Ga-labeled radiotracers.

METHODS

The radiolabeling precursor NOTA-SDG was designed to conjugate the targeting group D-glucose and the chelator NOTA with a propargylglycine linker. [68Ga]Ga-NOTA-SDG was obtained by incubation of 68Ga3+ and the precursor NOTA-SDG at 37 °C for 15 min. The in vitro stability of [68Ga]Ga-NOTA-SDG in PBS and mouse serum was studied using high-performance liquid chromatography with a radioactivity detector. The uptake mechanism of [68Ga]Ga-NOTA-SDG entry into U87 and A549 cells was investigated by co-incubation the radiotracer with different doses of D-glucose and insulin. PET imaging studies in mice bearing various tumors were performed to evaluate the in vivo tumor diagnostic capability of [68Ga]Ga-NOTA-SDG.

RESULTS

[68Ga]Ga-NOTA-SDG was obtained rapidly within 15 min with radiochemical yield (RCY) of ≥98 % and radiochemical purity (RCP) of ≥99 %. The probe exhibited high stability in mouse serum and PBS over a period of 2 h. Cellular uptake studies demonstrated that the entry of [68Ga]Ga-NOTA-SDG into tumor cells was mediated by glucose transporters, although the mechanism differs from that of D-glucose. PET imaging results indicated that [68Ga]Ga-NOTA-SDG showed high uptake in a variety of tumors (U87, A549, PC3 and A375), enabling clear visualization of the tumors. Moreover, it had lower uptake in non-target tissues compared with [18F]FDG.

CONCLUSIONS

[68Ga]Ga-NOTA-SDG has the potential to serve as a broad-spectrum PET imaging agent for clinical tumor diagnosis.

Diagnostic Performance of FAPI PET/CT for the Detection of Lymph Node Metastases in Lung Cancer Patients: A Meta-analysis

OBJECTIVE

To evaluate the diagnostic performance of fibroblast activation protein inhibitors (FAPI) PET/CT for the detection of lymph node (LN) metastases in lung cancer patients.

METHODS

The PubMed and Embase databases were searched to identify relevant articles published through July 2024. We included studies reporting the diagnostic accuracy of FAPI PET/CT in detecting LN metastases in lung cancer patients. A head-to-head comparison of FAPI PET/CT and fluorodeoxyglucose (FDG) PET/CT was made among available studies. The pooled sensitivity, specificity, and area under the summary receiver-operating characteristics curve (AUC) were determined by using bivariate random-effects model.

RESULTS

Seven studies with 409 patients were eligible. The pooled sensitivity, specificity, and AUC value for FAPI PET/CT in detecting LN metastases in lung cancer patients were 88% (95% CI, 78-93%), 94% (95% CI, 89-96%), and 0.97 (95% CI, 0.95-0.98), respectively. Six studies provided head-to-head comparison data, and the pooled sensitivity, specificity, and AUC value were 89% (95% CI 80-95%), 94% (95% CI 89-97%), and 0.97 (95% CI 0.95-0.98) for FAPI PET/CT versus 78% (95% CI 64-87%), 66% (95% CI 33-88%), and 0.80 (95% CI 0.76-0.83) for FDG PET/CT. Fagan nomogram indicated that when the pre-test probability was set at 26%, the negative post-test probability for a FAPI PET/CT scan could decrease to 4%.

CONCLUSIONS

FAPI PET/CT shows excellent diagnostic accuracy for the detection of LN metastases in lung cancer patients, and is superior to standard-of-care FDG PET/CT. The outstanding ruling-out performance of FAPI PET/CT for LN metastases indicates that it holds the potential to reduce invasive diagnostic procedures.

Molecular Engineering of Glycoaptamer Dual-Target Radionuclide Probes for PET/CT Imaging of Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is one of the most malignant cancer types, characterized by a lack of efficient diagnostic and treatment methods in clinical practice. The development of effective targeted diagnosis and treatment for TNBC has become an important research focus. Here, we report the first proof-of-concept evidence of a glycoaptamer dual-target radionuclide probe (GDRP) for positron emission tomography/computed tomography (PET/CT) imaging of TNBC. The GDRP was created through precise molecular engineering of the aptamer AS1411, combined with three mannose ligands. The GDRP exhibited significantly increased serum stability and a high affinity for TNBC cells through a dual targeting mode. The advantages of our developed GDRP were further demonstrated by its excellent in vivo PET/CT dynamic imaging performance, featuring a long imaging window and high spatiotemporal resolution. This flexible method allows for the preparation of glycosylated functional nucleic acid molecular probes with high serum stability and tumor specificity. We anticipate that this PET/CT molecular probe will expand the development of glycoaptamer-based radioactive drugs and provides molecular tools for the clinical diagnosis of TNBC.

Improved diagnosis of small cervical lymph node metastasis using postvascular phase perfluorobutane CEUS in cancer patients

BACKGROUND

Accurate identification of small metastatic lymph nodes (LNs) remains a significant challenge with conventional ultrasound (US) due to its limitations in sensitivity for smaller LNs. The use of contrast-enhanced ultrasound (CEUS), especially with perfluorobutane in the postvascular phase of CEUS, may improve the diagnosis of metastatic LNs in cancer patients. We sought to investigate the diagnostic accuracy of the postvascular phase of CEUS with perfluorobutane in identifying suspected small cervical LNs in cancer patients.

METHODS

This prospective study enrolled consecutive cancer patients with small cervical LNs suspected to be malignant on US from May 2023 to January 2024. All patients underwent CEUS with perfluorobutane injection, followed by observation during the vascular (6-60 s) and postvascular (10-30 min) phases before biopsy. The reference standard was histological assessment of the LNs through biopsy. The US and CEUS features were analyzed to assess the diagnostic performance of the US, vascular phase-CEUS, and postvascular phase-CEUS features, as well as their association with LN size.

RESULTS

The final dataset included 229 participants (mean age, 57 years ± 11 [SD] [range, 28-80]; 121 women) with 229 suspected LNs, including 125 metastatic and 104 benign LNs. Hypo-enhancement or no enhancement in the postvascular phase of CEUS show excellent sensitivity (97%) and a high negative predictive value (93%). The area under the receiver operating characteristic (ROC) curve of postvascular phase-CEUS is 0.763, significantly higher than that for US (0.574; P < 0.001). Compared to US and vascular phase-CEUS, postvascular phase-CEUS demonstrates superior sensitivity (P = 0.022, and < 0.001, respectively) and accuracy (P < 0.001, all) for diagnosing LNs, irrespective of LN size.

CONCLUSIONS

Postvascular phase-CEUS exhibited excellent diagnostic performance in identifying suspected small LNs in cancer patients. Hyper- or isoenhancing small LNs in the postvascular phase of CEUS were unlikely to be malignant, possibly obviating biopsy.

Low false-positive lymph nodes for 18 F-fibroblast activation protein inhibitors PET/computed tomography in preoperative staging of patients with nonsmall cell lung cancer

OBJECTIVE

This study aimed to evaluate the diagnostic accuracy of 18 F-fibroblast activation protein inhibitor (FAPI) PET/computed tomography (CT) in identifying primary tumors and mediastinal lymph node metastases in nonsmall cell lung cancer (NSCLC), with histopathological findings serving as the reference standard.

METHODS

Nineteen patients underwent preoperative 18 F-FAPI PET/CT and subsequent surgery; of these, 13 also underwent 18 F-fluorodeoxyglucose (FDG) PET/CT within 1 week. The diagnostic accuracy of primary tumors and lymph node metastases was evaluated for both modalities. Semiquantitative parameters, including maximum standardized uptake values (SUV max ) and target-to-background ratios (TBRs), for both primary tumors and lymph node metastases were assessed for both modalities.

RESULTS

For primary tumors, 18 of 19 (94.7%) showed positive results on 18 F-FAPI PET/CT scans. In 13 patients who also underwent 18 F-FDG PET/CT, 18 F-FAPI PET/CT demonstrated a higher detection rate compared with 18 F-FDG PET/CT (100% vs. 69.1%). The overall accuracy of lymph node assessment with 18 F-FAPI PET/CT (95.9-97.1%) was significantly higher compared to 18 F-FDG PET/CT (51.0%). Malignant lymph nodes exhibited significantly higher SUV max and TBR on 18 F-FAPI scans (SUV max : 7.0 vs. 0.9, P  < 0.001; TBR muscle : 5.0 vs. 0.8, P  < 0.001) than on 18 F-FDG scans (SUV max : 3.9 vs. 1.8, P  = 0.01), except for the liver TBR on 18 F-FDG scans (TBR liver : 1.8 vs. 1.0, P  = 0.055).

CONCLUSION

18 F-FAPI could be utilized in the preoperative staging of NSCLC to mitigate the incidence of false positives associated with 18 F-FDG, due to its higher accuracy in identifying mediastinal lymph node metastasis.

Current status of FAP-directed cancer theranostics: a bibliometric analysis

Fibroblast activation protein (FAP) is a key molecule in the field of oncology, with significant impacts on tumor diagnosis and treatment. Importantly, it has paved the way for the development of radiotracers for quinoline-based FAP inhibitors (FAPIs), which are currently among the most promising radiotracers for PET imaging in cancer. We performed a bibliometric analysis of scientific publications related to FAP and FAPI-based radiotracers, which included the quantification and visualization of current research trends and prospects based on various bibliometric indicators. In our survey of FAP-related studies in the Web of Science Core Collection databases, R and VOSviewer were used for visualization and bibliometric analyses based on country, institute, author, journal, and keywords. We also examined the methodology, radionuclide type, imaging instruments, and major diseases associated with studies on FAPI-based radiotracers. The results revealed 2,664 FAP-related publications from 1992 to the present. Germany, the USA, and China dominated paper publications, multinational collaborations, and societal impacts on FAP research. Southwest Medical University was the most productive institute, while Haberkorn Uwe authored the most cited papers and the highest H-index. The European Journal of Nuclear Medicine and Molecular Imaging and the Journal of Nuclear Medicine were the most influential periodicals. Keywords "FAP", "68Ga-FAPI", and "PET/CT" emerged as the most significant in this field. This study may help elucidate current research trends, hotspots, and directions for future research.

Value of [68Ga]Ga-NYM046 PET/CT, in Comparison with 18F-FDG PET/CT, for Diagnosis of Clear Cell Renal Cell Carcinoma

This study aimed to investigate the diagnostic efficacy of [68Ga]Ga-NYM046 PET/CT in animal models and patients with clear cell renal cell carcinoma (ccRCC) and to compare its performance with that of 18F-FDG PET/CT. Methods: The in vivo biodistribution of [68Ga]Ga-NYM046 was evaluated in mice bearing OS-RC-2 xenografts. Twelve patients with ccRCC were included in the study; all completed paired [68Ga]Ga-NYM046 PET/CT and 18F-FDG PET/CT. The diagnostic efficacies of these 2 PET tracers were compared. Moreover, the positive rate of carbonic anhydrase IX in the pathologic tissue sections was compared with the SUVmax obtained by PET/CT. Results: The tumor accumulation of [68Ga]Ga-NYM046 at 1 h after injection in OS-RC-2 xenograft tumor models was 7.21 ± 2.39 injected dose per gram of tissue. Apart from tumors, the kidney and stomach showed high-uptake distributions. In total, 9 primary tumors, 96 involved lymph nodes, and 147 distant metastases in 12 patients were evaluated using [68Ga]Ga-NYM046 and 18F-FDG PET/CT. Compared with 18F-FDG PET/CT, [68Ga]Ga-NYM046 PET/CT detected more primary tumors (9 vs. 1), involved lymph nodes (95 vs. 92), and distant metastases (137 vs. 127). In quantitative analysis, the primary tumors' SUVmax (median, 13.5 vs. 2.4; z = -2.668, P = 0.008) was significantly higher in [68Ga]Ga-NYM046 PET/CT. Conversely, the involved lymph nodes' SUVmax (median, 5.9 vs. 7.6; z = -3.236, P = 0.001) was higher in 18F-FDG PET/CT. No significant differences were found for distant metastases (median SUVmax, 5.0 vs. 5.0; z = -0.381, P = 0.703). Higher [68Ga]Ga-NYM046 uptake in primary tumors corresponded to higher expression of carbonic anhydrase IX, with an R 2 value of 0.8274. Conclusion: [68Ga]Ga-NYM046 PET/CT offers a viable strategy for detecting primary tumors, involved lymph nodes, and distant metastases in patients with ccRCC.

Head to head comparison of 18F-FDG and Al18F-NOTA-FAPI-04 PET/CT imaging used in diagnosis of autoimmune rheumatic diseases

OBJECTIVES

The aim of this study was to determine the performance of radionuclide-labeled fibroblast activation protein inhibitors (Al18F-NOTA-FAPI-04) PET/CT in patients with autoimmune rheumatic diseases (ARDs) and compare it with fluorine-18 (18F) labeled fluorodeoxyglucose (FDG) imaging.

METHODS

Fifty-eight participants with ARDs were prospectively enrolled from April 2022 to February 2024 and underwent dual-tracer PET/CT imaging. For both 18F-FDG and Al18F-NOTA-FAPI-04 PET/CT, imaging findings were interpreted and compared. The clinical significance was compared between18F-FDG PET/CT and Al18F-NOTA-FAPI-04 PET/CT imaging.

RESULTS

18F-FDG imaging was positive in 53 out of 58 cases (91.4%) while Al18F-NOTA-FAPI-04 imaging was positive in 55 out of 58 cases (94.8%). Overall positive rate of Al18F-NOTA-FAPI-04 imaging was as high as 18F-FDG imaging (P = 0.625). 18F-FDG imaging detected more lesions in lymph node, spleen, and bone marrow. Al18F-NOTA-FAPI-04 imaging detected more lesions in the lung, muscle, and tendon/ligament. There was no statistical difference of composing ratio of grades of clinical significance between two imaging modalities (χ2 = 2.875, P = 0.238). The superior rate of Al18F-NOTA-FAPI-04 PET/CT imaging was higher than 18F-FDG imaging (P = 0.020). In subgroup of adult-onset Still's disease, 18F-FDG imaging showed better performance than Al18F-NOTA-FAPI-04 imaging. In most of the other subgroup of ARDs, Al18F-NOTA-FAPI-04 PET/CT imaging overperformed 18F-FDG imaging.

CONCLUSION

Both 18F-FDG and Al18F-NOTA-FAPI-04 PET/CT imaging have excellent sensitivity in ARDs. The detection capabilities of two tracers varied according to the involving organs of ARDs. In most of ARDs except adult-onset Still's disease, Al18F-NOTA-FAPI-04 PET/CT imaging overperformed 18F-FDG imaging. Key Points • 18F-FDG and Al18F-NOTA-FAPI-04 PET/CT imaging have excellent sensitivity in diagnosing of ARDs. • 18F-FDG PET/CT imaging detected more lesions in lymph node, spleen, and bone marrow. • 18F-NOTA-FAPI-04 PET/CT imaging detected more lesions in the lung, muscle, and tendon/ligament. • 18F-NOTA-FAPI-04 PET/CT imaging overperformed18F-FDG in most subgroups of ARDs.

[68Ga]Ga-FAPI-46 PET/CT for Staging Suspected/Confirmed Lung Cancer: Results on the Surgical Cohort Within a Monocentric Prospective Trial

BACKGROUND/OBJECTIVES

To evaluate T&N-staging diagnostic performance of [68Ga]Ga-FAPI-46 PET/CT (FAPI) in a suspected/confirmed lung cancer surgical cohort.

METHODS

Patients were enrolled in a prospective monocentric trial (EudraCT: 2021-006570-23) to perform FAPI, in addition to conventional-staging-flow-chart (including [18F]F-FDG PET/CT-FDG). For the current purpose, only surgical patients were included. PET-semiquantitative parameters were measured for T&N: SUVmax, target-to-background-ratios (using mediastinal blood pool-MBP, liver-L and pulmonary-parenchyma-P). Visual and semiquantitative T&N PET/CT performances were analysed per patient and per region for both tracers, with surgical histopathology as standard-of-truth.

RESULTS

63 FAPI scans were performed in 64 patients enrolled (26 May 2022-30 November 2023). A total of 50/63 patients underwent surgery and were included. Agreement (%) with histopathological-T&N-StagingAJCC8thEdition was slightly in favour of FAPI (T-66% vs. 58%, N-78% vs. 70%), increasing when T&N dichotomised (T-92% vs. 80%, N-78% vs. 72%). The performance of Visual-Criteria for T-per patient (n = 50) resulted higher FAPI than FDG. For N-per patient (n = 46), sensitivity and NPV were slightly lower with FAPI. Among 59 T-regions surgically examined, malignancy was excluded in 6/59 (10%). FAPI showed (vs. FDG): sensitivity 85% (vs. 72%), specificity 67% (vs. 50%), PPV 96% (vs. 93%), NPV 33% (vs. 17%), accuracy 83% (vs. 69%). Among 217 N-stations surgically assessed (overall 746 ln removed), only 15/217 (7%) resulted malignant; FAPI showed (vs. FDG): sensitivity 53% (vs. 60%), PPV 53% (vs. 26%), NPV 97% (vs. 97%), and significantly higher specificity (97% vs. 88%, p = 0.001) and accuracy (94% vs. 86%, p = 0.018). Semiquantitative-PET parameters performed similarly, better for N (p < 0.001) than for T, slightly in favour (although not significantly) of FAPI over FDG.

CONCLUSIONS

In a suspected/confirmed lung cancer surgical cohort, PET/CT performances for preoperative T&Nstaging were slightly in favour of FAPI than FDG (except for suboptimal N-sensitivity), significantly better only for N (region-based) specificity and accuracy using visual assessment. The trial's conventional follow-up is still ongoing; future analyses are pending, including non-surgical findings and theoretical impact on patient management.

Role of [18F]FAPI-04 in staging and therapeutic management of intrahepatic cholangiocarcinoma: prospective comparison with [18F]FDG PET/CT

BACKGROUND

Fluorine-18 fluorodeoxyglucose ([18F]FDG) positron emission tomography/computed tomography (PET/CT) has some limitations in diagnosis of Intrahepatic cholangiocarcinoma (ICC).

MATERIALS AND METHODS

Patients with histologically confirmed ICC who underwent both [18F]FDG and 18F-labeled fibroblast-activation protein inhibitors ([18F]FAPI)-04 PET/CT were prospectively analyzed. The maximum standard uptake value (SUVmax), tumor-to-background ratio (TBR), metabolic tumor volume (MTV), total lesion glycolysis (TLG), [18F]FAPI-avid tumor volume (FTV), total lesion fibroblast activation protein expression (TLF) were compared between the two modalities by paired Wilcoxon signed-rank test and Mann-Whitney U test, and McNemar's test was used to assess the diagnostic accuracy between the two techniques.

RESULTS

In total, 23 patients with 389 lesions were included. Compared to [18F]FDG, [18F]F-FAPI-04 PET/CT demonstrated a higher detection rate for intrahepatic lesions (86.3% vs. 78.2% P = 0.040), lymph node metastases (85.2% vs. 68.2%, P = 0.007), peritoneal metastases (100% vs. 93.8%), and bone metastases (100% vs. 70.5%, P < 0.001). [18F]FAPI-04 PET showed higher SUVmax, TBR and greater tumor burden values than [18F]FDG PET in non-cholangitis intrahepatic lesions (SUVmax: 8.7 vs. 6.4, P < 0.001; TBR: 8.0 vs. 3.5, P < 0.001; FTV vs. MTV: 41.3 vs. 12.4, P < 0.001; TLF vs. TLG: 223.5 vs. 57.0, P < 0.001), lymph node metastases (SUVmax: 6.5 vs. 5.5, P = 0.042; TBR: 5.4 vs. 3.9, P < 0.001; FTV vs. MTV: 2.0 vs. 1.5, P = 0.026; TLF vs. TLG: 9.0 vs. 7.8 P = 0.024), and bone metastases (SUVmax: 9.7 vs. 5.25, P < 0.001; TBR: 10.8 vs. 3.0, P < 0.001; TLF vs. TLG: 9.8 vs. 4.2, P < 0.001). However, [18F]FDG showed higher radiotracer uptake (SUVmax: 14.7 vs. 8.4, P < 0.001; TBR: 7.4 vs. 2.8, P < 0.001) than [18F]FAPI-04 PET/CT for 6 patients with obstructive cholangitis. [18F]FAPI-04 PET/CT yielded a change in planned therapy in 6 of 23 (26.1%) patients compared with [18F]FDG.

CONCLUSIONS

[18F]FAPI-04 PET/CT had higher detection rate and radiotracer uptake than [18F]FDG PET/CT in intrahepatic lesions, lymph node metastases, and distant metastases, especially in bone. Therefore, [18F]FAPI-04 PET/CT may be a promising technique for diagnosis and staging of ICC.

TRIAL REGISTRATION

Clinical Trials, NCT05485792. Registered 1 August 2022, retrospectively registered, https//clinicaltrials.gov/study/NCT05485792?cond=NCT05485792&rank=1.

Mapping knowledge structure and themes trends of cancer-associated fibroblasts: a text-mining study

Introduction: Cancer-associated fibroblasts (CAFs) constitute an important component of the tumor microenvironment, participating in various facets of cancer advancement and being recognized as contributors to tumor immune evasion. The role of CAFs in various tumor types has attracted increasing attention recently. In this work, we conducted a comprehensive bibliometric analysis to uncover research trajectories and highlight emerging areas in the field of CAFs. Methods: A systematic search was performed within the Web of Science Core Collection to identify articles/reviews on CAFs published between 2000 and 2023. Leveraging advanced bibliometric tools such as VOSviewer, CiteSpace, and online website, we examined and visualized publication trends, geographic contributions, institutional affiliations, journal prominence, author collaborations, and noteworthy references, keywords, and genes. Results: Our analysis included 5,190 publications, indicating a rapid growth trend in both annual publications and citations related to CAFs. China and the United States emerged as the foremost contributors in terms of publications, funding agencies, and international collaborations. Breast cancer was the most studied tumor, followed by colorectal cancer, pancreatic cancer, prostate cancer, and gastric cancer. Based on co-occurrence and bursting keywords, we identified the following research topics including immune cells (T cells, B-cells, tumor-associated macrophages), tumor immune microenvironment (antitumor immunity, immune infiltration, immunosuppression), immunotherapy (PD-L1), microRNAs (miRNA), extracellular vesicles (exosome), multiple tumors (pancreatic ductal adenocarcinoma, bladder cancer, head and neck squamous cell carcinoma), antitumor agents (gemcitabine, cisplatin resistance), bioinformatics (pan-cancer), epithelial-mesenchymal transition (stemness), FAPI PET/CT, DNA methylation, etc., may receive sustained attention in the future. Furthermore, TGFB1, IL-6, TNF, TP53, and VEGFA emerged as the top 5 genes that have garnered the greatest research attention in the field of CAFs. The KEGG enrichment analysis highlighted that the top 20 most studied genes were mainly associated with HIF-1 and Toll-like receptor signaling pathways. Discussion: In sum, our bibliometric analysis offers a comprehensive overview of the research landscape in the field of CAFs. It encompasses the current state, evolving patterns, and prospective avenues of exploration, with special attention to the potential advancements in tumor immune microenvironment.