Comparison of [68Ga]Ga-DOTA-FAPI-04 and [18F] FDG PET/CT for the diagnosis of primary and metastatic lesions in patients with various types of cancer

Superiority of 68Ga-DOTA-FAPI-04 PET/CT to 18F-FDG PET/CT in the evaluation of different cancers with bone metastases

BACKGROUND

68Ga-DOTA-FAPI-04 is a new positron imaging agent, and its application in bone metastasis has been limited. The purpose of this retrospective study was to compare the diagnostic ability of 68Ga-DOTA-FAPI-04 PET/CT and 18F-FDG PET/CT to detect bone metastases in patients with different types of cancer.

METHODS

A total of 293 patients with pathologically confirmed primary malignancies were examined with 68Ga-DOTA-FAPI-04 PET/CT and 18F-FDG PET/CT within one week. Using pathological examination or follow-up CT or MRI scan as the gold standard, the diagnostic efficacy of the two methods in differentiating bone metastases was compared (p < 0.05, with statistical significance). The maximum standard uptake value (SUVmax) of the two methods for different types of bone metastasis was further compared. The SUVmax was used to compare the differences between the two methods in detecting bone metastases in different tumor types and different sites.

RESULTS

A total of 48 patients were diagnosed with bone metastasis, and 245 patients without bone metastasis. There were 376 bone metastases and 243 benign bone lesions. 68Ga-DOTA-FAPI-04 PET/CT and 18F-FDG PET/CT detected 376 and 228 metastases, respectively. Sensitivity, specificity, positive and negative predictive value (PPV and NPV) and accuracy of 68Ga-DOTA-FAPI-04 PET/CT and 18F-FDG PET/CT were 100.0 % vs 60.6 %, 93.8 % vs 99.2 %, 96.2 % vs 99.2 %, 100.0 % vs 62.0 % and 97.6 % vs 75.8 %, respectively. Compared with 18F-FDG, 68Ga-DOTA-FAPI-04 uptake was significantly increased in both benign bone lesions and metastases (p = 0.001). The uptake of 68Ga-DOTA-FAPI-04 for osteoblastic metastasis was also significantly higher than that of 18F-FDG (p < 0.001). In bone metastasis of lung cancer and gastric cancer, 68Ga-DOTA-FAPI-04 uptake was higher than that of 18F-FDG PET/CT (p < 0.05). Using SUVmax = 4.1 and SUVmax = 6.2 as the cutoff value by 68Ga-DOTA-FAPI-04 PET/CT and 18F-FDG PET/CT, it was possible to predict the occurrence of metastases (AUC = 0.817,95 % CI: 0.791-0.923 vs AUC =0.751,95%CI:0.626-0.875).

CONCLUSIONS

68Ga-DOTA-FAPI-04 as a novel imaging agent, can detect more bone metastases and has a higher tracer uptake level than 18F-FDG. Especially for lung and gastric cancer, 68Ga-DOTA-FAPI-04 PET/CT may be a more reliable means to detect bone metastases.

Comparison of [99mTc]Tc-FAPI SPECT/CT and [18F]FDG PET/CT as predictive biomarkers for immunotherapy response in gastrointestinal cancer

To explore the diagnostic performance of [99mTc]Tc-FAPI SPECT/CT for gastrointestinal cancer, compared to [18F]FDG PET/CT. In this analysis of a prospective trial, consecutively recruited patients from a single center with pathologically confirmed gastrointestinal cancer were prospectively enrolled from September 2022 to June 2024 and underwent paired v and [18F]FDG PET/CT examinations at intervals of more than 1 day and within 7 days of each other.The activity of tracer accumulation in lesions was assessed by maximum standardized uptake value(SUVmax) and TBR (lesions SUVmax/ascending aorta SUVmean). Histopathologic and clinical follow-up results were used as reference standards for final diagnoses. Seventy-eight patients (46 men; median age, 58.8 ± 14.5 years) were evaluated. Compared with the TBR for [18F]FDG uptake, TBR for [99mTc]Tc-FAPI uptake was higher in primary tumor(4.6 ± 2.0 vs. 3.4 ± 1.7; P = 0.001) ,peritoneal spread (1.3 [1.1,7.3] vs. 1.1[1.1,1.1]; P = 0.001 ) and liver metastases( 2.5[1.1,8.5] vs. 1.1[1.1,3.4]; P = 0.031). For diagnostic accuracy in a total of 253 lesions in 78 patients, compared with [18F]FDG PET/CT, [99mTc]Tc-FAPI SPECT/CT demonstrated a higher sensitivity (100% [15 of 15 lesions] vs. 20% [3 of 15]; P < 0.001), accuracy (100% [48 of 48 lesions] vs. 75% [36 of 48];P < 0.001), and negative predictive value (100% [33 of 33 lesions] vs. 69% [36 of 48 lesions]; P = 0 0.001) in detecting peritoneal spread, and a higher sensitivity (85% [17 of 20 lesions] vs. 50% [10 of 20]; P = 0.041) in detecting liver metastases. Patients with metastatic gastrointestinal carcinomas negative on the [99mTc]Tc-FAPI scan showed improved clinical prognosis after immunotherapy (P<0.006). TBR-FDG/TBR-FAPI was the main predictor of better prognosis post-immunotherapy ([stable disease, SD]+[partial response, PR]), with an optimal cut-off of 3.82. [99mTc]Tc-FAPI SPECT/CT can better evaluate peritoneal spread and liver metastases in gastrointestinal cancer. Furthermore, TBR-FDG/TBR-FAPI is a valuable imaging parameter for monitoring immunotherapy responses.

Detecting radiation esophagitis using 18F-FAPI-04 PET/CT in patients with LA-ESCC treated with concurrent chemoradiotherapy

PURPOSE

This prospective study examined whether 18F-AlF-NOTA-fibroblast activation protein inhibitor (FAPI)-04 (denoted as 18F-FAPI-04) positron emission tomography/computed tomography (PET/CT) can detect the development and severity of radiation esophagitis (RE) in patients with locally advanced esophageal squamous cell carcinoma (LA-ESCC) treated with concurrent chemoradiotherapy.

MATERIALS AND METHODS

From June 2021 to March 2022, images were collected from LA-ESCC patients who underwent 18F-FAPI-04 PET/CT examinations before and during radiotherapy. The development of RE was evaluated weekly according to Radiation Therapy Oncology Group criterion. The target-to-background ratio in blood (TBRblood) was analyzed at each time point and correlated with the onset and severity of RE. Factors that predicted RE were identified by multivariate logistic analyses.

RESULTS

Thirty patients were evaluated. Significantly higher TBRblood (during radiotherapy, P = 0.003) and change in TBRblood compared with pre-RT (ΔTBRblood, P = 0.002) were observed in patients with RE than patients without RE. Those with grade 3 RE had a significantly higher TBRblood (during radiotherapy, P = 0.003) and ΔTBRblood (P = 0.003) compared with those with RE < grade 3. On multivariate analysis, ΔTBRblood was identified as a significant detection of any grade RE (P = 0.021) and grade 3 RE (P = 0.038).

CONCLUSION

The ΔTBRblood on 18F-FAPI-04 PET/CT may be effective at identifying patients with RE, especially grade 3 RE.

Revolutionizing cancer diagnosis and dose biodistribution: a meta-analysis of [68ga] FAPI- 46 vs. [18f] FDG imaging

BACKGROUND

Advancements in novel peptides significantly affect cancer diagnosis by targeting cancer-specific markers, thereby improving imaging modalities, such as positron emission tomography combined with computed tomography (PET/CT) for more accurate tumor detection. This systematic review and meta-analysis aimed to assess the diagnostic accuracy of [18F] Fluorodeoxyglucose (FDG) and 68Ga-fibroblast activation protein inhibitor (FAPI- 46) PET/CT for early cancer detection.

METHODS

A comprehensive search was conducted in Scopus, MEDLINE, Web of Science, and Embase databases up to March 28, 2024, using MeSH keywords. Titles and abstracts were screened to identify studies on hybrid [68Ga] FAPI- 46 and [18F] FDG, followed by a detailed full-text evaluation. Only cohort or cross-sectional studies published in English, focusing on the clinical diagnosis of cancer patients, were included, while reviews, case reports, conference proceedings, and abstracts were excluded. Random-effects meta-analysis was used for the estimation of pooled specificity and sensitivity with 95% confidence intervals (CIs). In addition, the heterogeneity was assessed across studies and subgroup meta-analyses for the detection rate via Stata.

RESULTS

Among the 615 retrieved studies, nine articles were incorporated in the present systematic review, with five (n = 144 patients) eligible for meta-analysis. For [68Ga] FAPI- 46, the pooled sensitivity and specificity compared with immunohistopathology were 0.96 (95% CI 0.84, 0.99) and 0.92 (95% CI 0.53, 0.99), respectively, with a positive likelihood ratio (LR +) of 4.41 (95% CI 1.64, 11.79) and a negative likelihood ratio (LR -) of 3.07 (95% CI 1.01, 9.37). For [18F] FDG, pooled sensitivity and specificity compared with immunohistopathology were 0.73 (95% CI 0.34, 0.93) and 0.83 (95% CI 0.57, 0.95), with an LR + of 12.73 (95% CI 1.43, 113.45) and an LR - of 0.32 (95% CI 0.11, 0.17). The pooled odds ratio for the detection rate on a per-lesion basis was 1.73 (95% CI 0.99, 3.02) for [68Ga] FAPI- 46 compared with [18F] FDG. The pooled weighted mean differences in the standardized uptake value (SUVmax) for primary tumor uptake and the tumor-to-background ratio (TBR) in [68Ga] FAPI- 46 vs. 18F-FDG were 4.40 (95% CI - 0.7, 9.5) and 6.18 (95% CI 1.74, 10.61), respectively. Moderate to high heterogeneity was noted because of the variations in patient selection, interpretation criteria, and scanning procedures.

CONCLUSIONS

This study revealed that [68Ga] FAPI- 46 outperforms [18F] FDG in cancer diagnosis, with higher sensitivity (0.96 vs. 0.73) and specificity (0.92 vs. 0.83). [Ga] FAPI- 46 improved tumor detection with higher SUVmax and TBR. While FDG had a higher LR +, its lower LR - highlighted more false negatives. Accordingly, [68Ga] FAPI- 46 exhibited superior accuracy and reliability than FDG in cancer diagnosis.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD 42023472270.

Design, Synthesis, and Evaluation of a Novel Positron Emission Tomography Tracer Targeting Fibroblast Activation Protein: From Bench to Bedside

FAPI-PET/CT has become a promising tool for cancer diagnosis. However, the pharmacokinetic properties of FAPI tracers need optimization. Here, we developed a novel FAPI tracer, [18F]AlF-NOTA-SP2A-FAPT, for cancer imaging. NOTA-SP2A-FAPT was successfully synthesized and radiolabeled with a high radiochemical purity. [18F]AlF-NOTA-SP2A-FAPT displayed satisfying stability, hydrophilicity, and affinity to FAP, as well as specific uptake in A549-FAP cells. Micro-PET/CT showed that [18F]AlF-NOTA-SP2A-FAPT is rapidly excreted through the renal system. [18F]AlF-NOTA-SP2A-FAPT exhibited high tumor uptake and excellent retention, showing better tumor delineation compared to [18F]FDG and [18F]AlF-NOTA-FAPI-42. Pilot clinical studies of [18F]AlF-NOTA-SP2A-FAPT and head-to-head comparison with [18F]FDG were performed on 13 cancer patients. Compared to [18F]FDG, [18F]AlF-NOTA-SP2A-FAPT had higher uptake in primary tumor and lymph node metastases as well as favorable distribution and good tumor retention. In conclusion, [18F]AlF-NOTA-SP2A-FAPT demonstrated high tumor accumulation, as well as improved pharmacokinetic properties. [18F]AlF-NOTA-SP2A-FAPT could emerge as a promising alternative to the currently established FAPI tracers.

One-Stop 68 Ga-FAPI/ 18 F-FDG Total-Body PET/CT Scan : More Theranostics Information Available

PURPOSE

This prospective study aims to assess the feasibility of a one-stop imaging protocol using 68 Ga-FAPI-04/ 18 F-FDG dual-radiotracer with dual-low-activity for tumor imaging.

PATIENTS AND METHODS

Forty patients underwent one-stop 68 Ga-FAPI-04 PET (PET FAPI ) and dual-radiotracer PET (PET DUAL ) using a total-body PET/CT scanner with a 194-cm axial field of view. After a half-dose (0.925 MBq/kg) 68 Ga-FAPI-04 PET/CT, an additional half-dose (1.85 MBq/kg) of 18 F-FDG was administered for a 60-minute dynamic acquisition. PET DUAL was reconstructed at 10-minute intervals (PET D0-10 , PET D10-20 , PET D20-30 , PET D30-40 , PET D40-50 , and PET D50-60 ). Data of lesion detectability, target-to-background ratios, tumor staging, and total radiation dose were analyzed. A target-to-liver ratio (TLR) ≥ 3 on PET FAPI was considered indicative of sufficient fibroblast activation protein expression.

RESULTS

PET D50-60 and PET FAPI showed similar performance in detecting primary tumors (42 vs 41, P  > 0.999). However, significantly more metastatic lesions were identified on PET D50-60 compared with PET FAPI (102 vs 60, P  < 0.001). PET FAPI demonstrated significantly higher TLR, target-to-blood-pool ratio, and target-to-normal-tissue ratio than PET DUAL ( P  < 0.05). Lesion detectability was similar across PET D10-20 , PET D20-30 , PET D30-40 , PET D40-50 , and PET D50-60 (all P 's > 0.05). Notably, PET D30-40 and PET D40-50 detected all lesions identified by PET D50-60 . PET D40-50 showed no significant differences in TLR, target-to-blood-pool ratio, and target-to-normal-tissue ratio compared with PET D50-60 ( P  > 0.05). Up to 94.9% of malignant primary lesions exhibited a TLR ≥ 3 on PET FAPI . The average effective dose was 9.85 ± 2.19 mSv, similar to that of a whole-body 18 F-FDG PET/CT.

CONCLUSIONS

This one-stop, dual-radiotracer, dual-low-activity imaging protocol combines the strengths of 68 Ga-FAPI-04 and 18 F-FDG, offering a shorter imaging duration and reduced radiation exposure.

Evaluating the diagnostic value of 18F-FAPI-04 PET/CT in various malignant tumors: a head-to-head comparison with 18F-FDG PET/CT

PURPOSE

This study aims to evaluate the diagnostic efficacy of 18F-fibroblast activation protein inhibitor-04 (18F-FAPI-04) PET/CT for various malignant tumors and compare it head-to-head with 18F-FDG PET/CT.

MATERIALS AND METHODS

This single-center, prospective study continuously recruited patients with suspected or confirmed malignant tumors for concurrent 18F-FDG and 18F-FAPI-04 PET/CT scans from April 2022 to October 2023. The pathological diagnosis or clinical follow-up served as the reference standard. The Z-test for two proportions was used to compare the sensitivity, specificity, and accuracy of tumor diagnosis between the two imaging agents. Wilcoxon signed-rank tests were employed to compare the uptake of the two radiotracers and the tumor-to-background ratio (TBR) differences in tumors.

RESULTS

The study involved 15 types of tumors and included 88 patients, comprising 53 males and 39 females, with an average age of 57.7 ± 10.8 years. In patient-based analysis, 18F-FAPI-04 PET/CT demonstrated higher diagnostic accuracy than 18F-FDG PET/CT for both initial staging and restaging patients (77.4% vs 56.6%, p = 0.0389; 94.3% vs 54.3%, p < 0.001), prompting treatment plan adjustments in 17% of restaged patients. The lesion-based analysis revealed comparable diagnostic accuracy of 18F-FAPI-04 PET/CT and 18F-FDG PET/CT for primary tumors (78.9% vs 75.4%, p = 0.8234), while showing superior accuracy for residual/recurrent tumors, lymph node metastases, and distant metastases compared to 18F-FDG PET/CT (100.0% vs 50.0%, p = 0.002; 98.8% vs 86.0%, p < 0.001; 98.3% vs 79.3%, p < 0.001).

CONCLUSION

18F-FAPI-04 PET/CT exhibits higher uptake and TBR in most tumors demonstrating superior diagnostic efficacy for primary lesions, residual/recurrent disease, and metastases compared to 18F-FDG PET/CT, particularly beneficial for restaging post-treatment patients.

The molar dose of FAPI administered impacts on the FAP-targeted PET imaging and therapy in mouse syngeneic tumor models

PURPOSE

Since fibroblast activation protein (FAP), one predominant biomarker of cancer associated fibroblasts (CAFs), is highly expressed in the tumor stroma of various epidermal-derived cancers, targeting FAP for tumor diagnosis and treatment has shown substantial potentials in both preclinical and clinical studies. However, in preclinical settings, tumor-bearing mice exhibit relatively low absolute FAP expression levels, leading to challenges in acquiring high-quality PET images using radiolabeled FAP ligands (FAPIs) with low molar activity, because of which a saturation effect in imaging is prone to happen. Moreover, how exactly the molar dose of FAPI administered to a mouse influences the targeted PET imaging and radiotherapy remains unclear now. Therefore, this study aims to investigate the impacts of the molar dose of the administered FAPI on FAP-targeted PET imaging and radiotherapy in mouse syngeneic tumor models.

METHODS

[68Ga]Ga-FAPI-04 with various molar doses of FAPI-04 was administered to wild-type 4T1 tumor-bearing mice, followed by static PET imaging. Sigmoidal curves were generated to analyze the correlation between the standard uptake value (SUV) and the administered molar doses of FAPI-04. Similarly, [177Lu]Lu-DOTAGA.(SA.FAPi)2 with a consistent dose of radioactivity but containing different moles of DOTAGA.(SA.FAPi)2 were injected into 4T1 tumor-bearing mice to assess the therapeutic effect. [68Ga]Ga-FAPI-04 was also applied to different tumor models for PET/CT imaging.

RESULTS

A gradient blocking effect was observed with increasing FAPI molar dose in [68Ga]Ga-FAPI-04 PET imaging and [177Lu]Lu-DOTAGA.(SA.FAPi)2 treatment, with various imaging and therapeutic outcomes. [68Ga]Ga-FAPI-04 PET exhibit potentials to characterize murine derived FAP expression with low molar dose of administered FAPI-04 using various tumor models.

CONCLUSION

The molar dose of FAPI in [68Ga]Ga/[177Lu]Lu-FAPI had a substantial impact on FAP-targeted imaging and therapy in mouse syngeneic tumor models. To acquire enhanced reliability and reproducibility in preclinical situation, it is critical to carefully consider the molar dose of the radiotracer when applying radiolabeled FAP ligands to FAP-targeted imaging and radiotherapy.

Physiological Uptake of 68Ga-FAPI-04 in Female Reproductive System

PURPOSE

Since the avid uptake of 68Ga-labeled fibroblast activation protein inhibitor (68Ga-FAPI-04) observed in female reproductive organs, our objectives were to investigate the physiological uptake characteristics and provide preliminary reference ranges for clinical use.

PROCEDURES

We reviewed the findings of female patients who underwent 68Ga-FAPI-04 PET/CT at our institution between April 2022 and June 2023. The standard uptake value (SUV) of reproductive organs and menstrual information were collected. All patients were categorized into reproductive period group, perimenopause group, and postmenopause group. We analysed the uptake levels among the three groups, and their association with age and menstrual cycle.

RESULTS

A total of 109 patients were included in this study. Higher ovarian SUVs were detected in reproductive patients (SUVright: 2.75 ± 0.84, IQR: 1.39-5.26; SUVleft: 2.72, IQR: 2.34-3.20; p = 0.315) than in postmenopausal patients (SUVright: 2.27, IQR: 2.01-2.75; SUVleft: 2.38 ± 0.55, IQR: 1.35-3.60; p = 0.767), as well as uterine 68Ga-FAPI-04 accumulations. The SUVs of uterine fundus and corpus were approximately three times higher than that of the cervix. In reproductive period group, higher SUVs were observed in bilateral ovaries around the ovulatory phase to the early luteal phase, and higher uterine SUVs were noted in the menstrual and proliferative phases. The SUVs in all reproductive organs (except the ovaries) showed significant negative correlations with age in all patients (all p < 0.01).

CONCLUSIONS

68Ga-FAPI-04 SUVs in reproductive organs are higher in premenopausal patients than in postmenopausal patients. The 68Ga-FAPI-04 accumulation in reproductive organs might be associated with menstrual cycle. Including more patients from different menstrual phases could contribute to investigating the uptake characteristics and their underlying mechanisms.

PET Imaging and Key Radiotracers for Evaluating Response to Locoregional Therapy in Hepatocellular Carcinoma

Locoregional therapies (LRTs) play a considerable role in the management of hepatocellular carcinoma (HCC), especially for patients who are not suitable for radical resection or transplantation. In clinical practice, assessment of LRTs is mainly based on computed tomography and MR imaging, but functional and metabolic information is less accessible. This article reviews the use of various the standardized uptake value parameters based on PET and multiple radiotracers for managing HCC after treatment with different LRTs, as well as parts of preclinical research. It discusses the current use of PET in more detail, as well as its advantages, disadvantages, and prospects.

Comparison of Al18F-NOTA-FAPI-74 and 18F-FDG PET/CT in the Evaluation and Staging of Hepatobiliary Malignancies: A Single-center Prospective Study

BACKGROUND

Accurate diagnosis and staging are crucial for the management of patients with hepatobiliary malignancies. Here, we investigated the efficacy of Al18F-NOTA-FAPI-74 PET/CT in detecting hepatobiliary malignancies and compared the results with 18F-FDG PET/CT.

PATIENTS AND METHODS

Participants with hepatobiliary malignancies were prospectively enrolled and underwent paired Al18F-NOTA-FAPI-74 and 18F-FDG PET/CT from April 2023 to March 2024. Histopathology and/or follow-up imaging served as the reference standard. The SUVmax of the primary and metastatic lesions between Al18F-NOTA-FAPI-74 and 18F-FDG PET/CT were compared using the Wilcoxon signed-rank test. The association between Al18F-NOTA-FAPI-74 uptake intensity and immunohistochemical FAP expression was analyzed with Spearman r correlation.

RESULTS

Our cohort comprised of 28 patients with hepatobiliary malignancies, including 12 with hepatocellular carcinoma, 13 with intrahepatic cholangiocarcinoma (ICC), 2 with perihilar cholangiocarcinoma, and 1 with gallbladder carcinoma. Of these 28 patients, 13 underwent PET/CT for initial staging and 15 for restaging. Al18F-NOTA-FAPI-74 PET/CT showed higher sensitivity than 18F-FDG PET/CT for detecting primary tumors [100% (13/13) vs 92.3% (12/13)], lymph node metastases [79.2% (42/53) vs 54.7% (29/53)], and bone and visceral metastases [97.6% (164/168) vs 69.0% (116/168)]. Al18F-NOTA-FAPI-74 PET/CT findings led to upstaging or restaging in 6 of 28 patients compared with the 18F-FDG PET/CT-based stage. In addition, Al18F-NOTA-FAPI-74 PET/CT detected tumor-related obstructive inflammation in 7 patients, while 18F-FDG PET/CT detected it in only 1 patient (25% vs 3.6%). All these 7 patients suffered from cholangiocarcinomas, including 5 with ICC and 2 with perihilar cholangiocarcinomas. The SUVmax of obstructive inflammation on Al18F-NOTA-FAPI-74 PET/CT was significantly lower than that of tumor (median SUVmax, 4.0 vs 8.8; P = 0.008). A positive correlation was found between FAPI uptake and FAP expression (r = 0.730, P = 0.04).

CONCLUSIONS

In patients with hepatobiliary malignancies, Al18F-NOTA-FAPI-74 PET/CT outperformed 18F-FDG PET/CT in detecting primary tumors and metastatic lesions, resulting in more accurate staging or restaging. In addition, Al18F-NOTA-FAPI-74 PET/CT showed good detection efficacy for tumor-related obstructive inflammation, which was only found in cholangiocarcinoma, thus rendering Al18F-NOTA-FAPI-74 the potential to differentiate ICC from hepatocellular carcinoma.

177Lu-LNC1004 Radioligand Therapy in Patients with End-stage Metastatic Cancers: A Single-Center, Single-Arm, Phase II Study

PURPOSE

Fibroblast activation protein (FAP) is highly expressed in cancer-associated fibroblasts and certain tumor cells, making it a promising therapeutic target for various malignancies. This study evaluated the efficacy and safety of 177Lu-Evans blue-FAP inhibitor (177Lu-LNC1004) radioligand therapy (RLT) for treating end-stage metastatic tumors.

PATIENTS AND METHODS

This single-arm, single-center, phase II trial included 28 patients with progressive metastatic malignancies (11 types) and high FAP expression (defined as a maximum standardized uptake value ≥10 in >50% of tumors) who had exhausted all approved therapies, screened between June 2022 and April 2024. Patients were scheduled to receive four 177Lu-LNC1004 RLT cycles at 3.33 GBq/cycle every 6 weeks. The primary endpoint was post-RLT radiologic response. The secondary endpoints were progression-free survival (PFS), overall survival (OS), dosimetry, and safety.

RESULTS

Eastern Cooperative Oncology Group scores >2 were observed in 68% of patients. Overall, 63 177Lu-LNC1004 RLT cycles were performed, with 19 (68%) patients undergoing ≥2 cycles. Disease control was achieved in 13 (13/28, 46%) patients, with 4 and 9 patients demonstrating partial response and stable disease, respectively, and associated with improved PFS and OS (P < 0.001). The mean absorbed dose in tumors was 4.69 ± 3.83 Gy/GBq (1.18-25.03 Gy/GBq). Treatment-related grade 3/4 hematotoxicity was observed in six (21%) patients, with thrombocytopenia, leukopenia, and neutropenia most prevalent. No grade 3/4 hepatotoxicity or nephrotoxicity was observed.

CONCLUSIONS

FAP-directed RLT using 177Lu-LNC1004 at 3.33 GBq/cycle was well tolerated with an acceptable toxicity profile. Nearly half of patients achieved disease control, which was associated with prolonged PFS and OS.

Exploring currently available fibroblast activation protein targeting molecules in adrenocortical carcinoma: Navigating theranostic pathways

INTRODUCTION

Cancer-associated fibroblasts (CAFs) expressing fibroblast activation protein (FAP) in the adrenocortical carcinoma (ACC) microenvironment may be used as potential therapeutic targets. This study investigated the diagnostic potential of four FAPi derivatives i.e. DOTA-FAPi-46 (FAPi46), DOTA.SA.FAPi (SA.FAPi), DATA5m.SA.FAPi (DATA.FAPi) and DATA5m.C4.FAPi (C4.FAPi) and compared with standard-of-care 18F-FDG (FDG) in ACC.

METHODS

Thirty histopathological proven cases of localized or metastatic ACC were recruited for both FDG and FAPi PET (number of patients (n) = 5 for SA.FAPi, n = 5 for DATA.FAPi, n = 5 for C4.FAPi and n = 15 for FAPi46). For biodistribution, standardized uptake values (SUV's) were computed by delineating region-of-interest on various body organs. For comparative analysis in disease identification, lesion tracer uptake was quantified using standardized uptake values corrected for lean body mass (SUL), tumor-to-background ratio (TBR), total lesion glycolysis (TLG for FDG) and total lesion FAP expression (TLF for FAPi).

RESULTS

In overall analysis, both FAPi and FDG PET exhibited comparable mean SULpeak [FAPi 4.3 (8.0-1.7) vs FDG 3.9 (8.1-2.5), p-0.271], mean SULavg [2.2 (4.3-1.2) vs 2.2 (3.4-1.3), p-0.897] and mean TBR [1.8 (3.2-1.2) vs 1.9 (2.7-1.2), p-0.696]. In volumetric analysis, comparable mean TLF and mean TLG was noted for the cohort [9.3 (53.7-4.5) vs 11.8 (33.0-4.3), p-0.107]. Sub-categorical analysis demonstrated complete concordant findings for both radiotracers in detection of all primary lesions, nodal lesions and distant metastases in lung and peritoneum with discordant findings in liver (22%) and skeletal lesions (33%). For lesion detection, DATA.FAPi and FAPi46 showed 100% concordance with FDG scan findings in metastatic disease. SA.FAPi exhibited 33% discordance by detecting an additional skeletal lesion, while C4.FAPi had 10% discordance, missing one liver lesion identified by FDG. Three 68 Ga-FAP derivatives (SA.FAPi, DATA.FAPi, and C4.FAPi) exhibited similar biodistribution, with uptake in the salivary glands, thyroid, liver, pancreas, muscles, and kidneys, and variable uptake in the lacrimal glands, extra-ocular muscles, oral mucosa, and uterus. In contrast, FAPi46 physiological expression was noted in salivary glands and muscles, with no uptake in other organs. Pancreatic uptake was highest for SA.FAPi (SUVmean 11.8), DATA.FAPi (12.1), and C4.FAPi (10.8), while FAPi46 had the lowest (1.7). Conversely, FAPi46 exhibited the highest muscle uptake (SUVmean 4.3) compared to SA.FAPi (1.7), DATA.FAPi (1.4), and C4.FAPi (1.0).

CONCLUSION

All the existing FAP inhibitor molecules were comparable to FDG PET for mapping disease spread and appeared as potential theranostic targets for the management of ACC.

A Meta-analysis of 68Ga-FAPI PET in Assessment of Ovarian Cancer

RATIONALE AND OBJECTIVES

The objective of this research is to carry out a systematic review and meta-analysis to detect the diagnostic efficacy of 68Ga-FAPI Positron Emission Tomography (PET) Computed Tomography/Magnetic Resonance (CT/MR) in total of the lesions as well as different aspects of metastasis in individuals with ovarian cancers (OC).

MATERIALS AND METHODS

The PubMed, Embase, Cochrane library, and Web of Science databases were thoroughly searched until the cut-off date of July 23, 2024. The assessment of 68Ga-FAPI PET CT/MR of OC was presented by the included studies. Bivariate random effects models were utilized to compute the sensitivity and specificity of 68Ga-FAPI PET CT/MR in OC. The I-square index (I2) was utilized to measure heterogeneity and sensitivity analysis were employed to test it.

RESULTS

The pooled sensitivity as well as specificity for 68Ga-FAPI PET CT/MR in OC were 0.90 (95% CI: 0.84-0.95) as well as 0.95 (95% CI: 0.91-0.97), correspondingly. In the subanalysis for metastatic lesions (lymph node [LN] metastases and peritoneal involvement), the pooled sensitivity and specificity of 68Ga-FAPI PET CT/MR were 0.94 (95% CI: 0.74-0.99) and 0.95 (95% CI: 0.84-0.99) for identifying metastatic LNs as well as 0.93 (95% CI: 0.81-0.97) and 0.96 (95% CI: 0.89-0.99) about peritoneal carcinomatosis evaluation, correspondingly. In the head-to-head comparison with 18F-FDG PET/CT, 68Ga-FAPI PET CT/MR exhibited a better sensitivity in identifying peritoneal metastases (P=.0004).

CONCLUSION

68Ga-FAPI PET CT/MR displayed a high overall diagnostic effectiveness in OC. When evaluating metastatic peritoneal lesions of OC, 68Ga-FAPI PET CT/MR displayed a superior pooled sensitivity.

Same-Day Positron Emission Tomography/Computed Tomography with 68Ga-Radiolabeled Fibroblast Activation Protein Inhibitors and 18F-Fluorodeoxyglucose Imaging for Gastrointestinal Cancers

Objective: We investigated the clinical practicability of same-day 68Ga-radiolabeled fibroblast activation protein inhibitors (68Ga-FAPI)-first and 18F-fluorodeoxyglucose (18F-FDG) imaging and compared it with same-day 18F-FDG-first or 2-day procedures in diagnosing gastrointestinal cancers. Materials and Methods: Sixty-five patients with confirmed gastrointestinal cancers were divided into same-day 68Ga-FAPI-first group (Group A), same-day 18F-FDG-first group (Group B), and 2-day group (Group C). Low-dose CT and low injection activity were performed on 68Ga-FAPI positron emission tomography/computed tomography (PET/CT). Interval times, radiation dose, diagnostic performance, and detectability were assessed among groups. Additionally, the uptake, tumor-to-liver ratio (TLR), diagnostic efficacy, and TNM stage were compared between the two modalities. Results: The total waiting time for Group C was significantly longer than that for Group A or B (both p < 0.001). The total dose-length product and effective dose decreased in all groups. There were comparable detectability and diagnostic performance among groups (all p > 0.05). The within-group analysis in Group B indicated that 68Ga-FAPI PET/CT had higher uptake in the primary and recurrent lesions than 18F-FDG without differences in TLR, due to higher liver background on 68Ga-FAPI PET than Group A or C (both p < 0.001).68Ga-FAPI PET/CT possessed higher accuracy than 18F-FDG and changed staging in 14 patients (14/65, 21.54%). Conclusions: The same-day 68Ga-FAPI-first and 18F-FDG imaging reduced examination waiting time without increased radiation dose, simultaneously achieving excellent diagnostic performance and improving clinical staging in diagnosing gastrointestinal cancers.

FAP-Targeted SPECT/CT and PET/CT Imaging for Breast Cancer Patients

ABSTRACT

Breast cancer presents a significant global health challenge, necessitating continued innovation in diagnostic and therapeutic approaches. Recent advances have led to the identification of cancer-associated fibroblasts, which are highly prevalent in breast cancers and express fibroblast activation proteins (FAPs), as critical targets. FAP-specific radiotracers, when used with PET/CT and SPECT/CT, have significant potential for improving early breast cancer detection, staging, treatment response monitoring, and therapeutic intervention. This review provides insight into FAP-targeted molecular imaging, exploring advanced techniques for protein status assessment, development of early-phase targeted therapies, and other emerging applications. The advent of FAP-targeted imaging stands to significantly enhance personalized oncologic care, leading to improved breast cancer management and overall patient outcomes.

Phase I study of [68Ga]Ga-HX01 for targeting integrin αvβ3 and CD13 in healthy and malignancy subjects

PURPOSE

Noninvasive angiogenesis visualization is essential for evaluating tumor proliferation, progression, invasion, and metastasis. This study aimed to translate the heterodimeric PET tracer [68Ga]Ga-HX01, which targets integrin αvβ3 and CD13 in neovascularization, into phase I clinical study.

METHODS

This study enrolled 12 healthy volunteers (phase Ia) and 10 patients with malignant tumors (phase Ib). The subjects in phase Ia were divided into low-dose (0.05 mCi/kg) and high-dose (0.1 mCi/kg) groups. For phase Ia subjects, PET/CT images, blood and urine samples were collected to analyze the biodistribution, pharmacokinetics, radiation dosimetry, and safety of [68Ga]Ga-HX01. For phase Ib patients, PET/MR scans were performed at 30 ± 5 and 60 ± 5 min after injection. The safety and preliminary diagnostic value of [68Ga]Ga-HX01 were assessed.

RESULTS

In phase Ia study, [68Ga]Ga-HX01 was distributed and metabolized similarly in two dosage groups as the highest accumulations in kidneys and urine. It possessed quick renal excretion and blood clearance with an elimination half-life (T1/2) of 28.92 ± 3.97 min. The total effective dose was 2.14 × 10- 2 mSv/MBq. In phase Ib study, [68Ga]Ga-HX01 clearly detected the lesions per patient, and found a total of 59 lesions with varying uptake levels. For safety evaluation, no serious adverse events were observed during the examination.

CONCLUSION

[68Ga]Ga-HX01 has proved to be a translational radiopharmaceutical with reliable security, favorable pharmacokinetics, and the ability to visualize tumors. The preliminary results in malignancy patients warrant further investigation of [68Ga]Ga-HX01 in monitoring antiangiogenic therapy of patients with malignancies.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, NCT06416774. Registered 11 May, 2024.

[68Ga]Ga-FAPI04 Outperforms [18F]FDG PET/CT for Detecting Nodal Metastasis of Head and Neck Squamous Cell Carcinoma: A Single-Center Experience

This study assesses fibroblast activated protein inhibitor (FAPI) targeted PET/CT imaging against [18F]FDG PET/CT (FDG PET) for detecting nodal involvement in head and neck squamous cell carcinoma (HNSCC), intending to improve diagnostic precision for metastatic lymph nodes and lay the groundwork for future investigations. Methods: Patients diagnosed with HNSCC were retrospectively enrolled. All patients underwent [68Ga]Ga-FAPI04 PET/CT (FAPI PET) and FDG PET within 6 d. Primary tumor, lymph nodes, and tracer uptake were visually and quantitatively compared. The metastatic lymph nodes were evaluated using patient-and lesion-based analyses, with biopsy or postoperative histopathological examination as the reference. Results: The cohort includes 24 patients (17 men, 7 women; mean age 60 ± 11.8 years) who underwent FDG and FAPI PET for preoperative diagnostic workup or restaging due to known recurrence of HNSCC. Lesions included 24 primary tumors, 54 cervical lymph nodes, and 5 metastases. Primary tumors exhibited significant uptake on both PET modalities (median maximum standardized uptake value [SUVmax]: FDG 19.4 ± 11.6, FAPI 16.9 ± 4.6), with no statistically significant difference (p > 0.5). For lymph nodes, FAPI and FDG PET showed median SUVmax of 9.18 ± 6.77 and 9.67 ± 6.5, respectively. The patient-based analysis found FDG PET sensitivity at 88.2% and FAPI PET at 94.1%, with FAPI PET specificity significantly higher (85.7% vs. 42.8% for FDG PET). Lesion-based analysis revealed FAPI PET sensitivity and specificity at 84.2% and 93.7%, respectively, contrasting FDG PET's at 81.5% and 25%, respectively. Conclusion: This study underscores the efficacy of FAPI PET in detecting primary tumors in HNSCC. Furthermore, FAPI PET shows improved specificity over FDG PET for metastatic lymph nodes advocating further investigations for integrating FAPI PET into HNSCC clinical protocols for its enhanced precision in detecting metastatic lymph nodes.

Xanthene-based NIR organic phototheranostics agents: design strategies and biomedical applications

Fluorescence imaging and phototherapy in the near-infrared window (NIR, 650-1700 nm) have attracted great attention for biomedical applications due to their minimal invasiveness, ultra-low photon scattering and high spatial-temporal precision. Among NIR emitting/absorbing organic dyes, xanthene derivatives with controllable molecular structures and optical properties, excellent fluorescence quantum yields, high molar absorption coefficients and remarkable chemical stability have been extensively studied and explored in the field of biological theranostics. The present study was aimed at providing a comprehensive summary of the progress in the development and design strategies of xanthene derivative fluorophores for advanced biological phototheranostics. This study elucidated several representative controllable strategies, including electronic programming strategies, extension of conjugated backbones, and strategic establishment of activatable fluorophores, which enhance the NIR fluorescence of xanthene backbones. Subsequently, the development of xanthene nanoplatforms based on NIR fluorescence for biological applications was detailed. Overall, this work outlines future efforts and directions for improving NIR xanthene derivatives to meet evolving clinical needs. It is anticipated that this contribution could provide a viable reference for the strategic design of organic NIR fluorophores, thereby enhancing their potential clinical practice in future.

Diagnostic Performance of Radiolabelled FAPI Versus [18F]FDG PET Imaging in Hepato-Pancreato-Biliary Oncology: A Systematic Review and Meta-Analysis

Radiolabelled fibroblast activation protein inhibitor (FAPI) tracers have the potential to overcome the limitations of 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) and improve the diagnosis and staging of hepato-pancreato-biliary (HPB) cancers. This study aims to compare the diagnostic performance of radiolabelled FAPI versus [18F]FDG PET imaging in HPB cancers. A systematic search of PubMed, Embase, Web of Science and Cochrane Library was performed to identify eligible studies on the diagnostic performance of FAPI PET for primary HPB tumours (hepatocellular carcinoma (HCC), pancreatic cancer (PC) and biliary tract cancer (BTC)) and for liver metastases of gastrointestinal origin. The diagnostic performance was defined as a combination of detection rate and semi-quantitative tracer uptake. A random-effects model was used to calculate the risk differences. In total, 28 studies were included. Histopathology was the reference standard for the primary tumour in 26 studies (93%). The detection rate of radiolabelled FAPI in comparison to [18F]FDG was significantly higher in HCC (0.33, 95% CI: 0.20-0.47 and 0.34, 95% CI: 0.23-0.45) and BTC (0.27, 95% CI: 0.11-0.43 and 0.28, 95% CI: 0.08-0.48), in the patient- and lesion-based analyses, respectively. In PC, no differences were observed. Radiolabelled FAPI outperformed [18F]FDG in the lesion-based detection of lymph node, liver and extra-hepatic metastases. In all HPB cancers, the mean SUVmax was significantly higher with radiolabelled FAPI compared to [18F]FDG. Molecular imaging with FAPI PET seems to have several benefits over [18F]FDG PET in HPB cancer diagnostics, with an overall higher tracer uptake, and higher detection rates in HCC and BTC.

Comparison of 68 Ga-FAPI and 18 F-FDG PET/CT Findings in Oncocytic and Conventional Subtypes of Pediatric Adrenocortical Carcinoma

ABSTRACT

Adrenocortical carcinoma, a poor prognosis cancer with a low survival rate, is a rare pediatric malignancy. We performed 18 F-FDG PET/CT and 68 Ga-FAPI PET/CT imaging in 2 children with different subtypes of adrenocortical carcinoma and compared the findings. FAPI PET/CT revealed superior performance in patient with conventional subtype and in detecting skeletal lesions. However, the recurrent lesions in the surgical bed had higher FDG uptake in both patients.

Comparison of Al[18F]-NOTA-FAPI-04 PET/CT and [18F]-FDG PET/CT in a patient with lung cancer and pulmonary tuberculosis: a case report and literature review

Background

The coexistence of lung cancer and pulmonary tuberculosis (TB) makes differential diagnosis even more complicated. The purpose of the study is to explore superiority of [18F]-NOTA-FAPI-04 PET/CT in distinguishing TB from malignant lesions and accurately detecting inflammatory lymph nodes than [18F]-FDG PET/CT.

Case summary

Herein, we described a case report of a patient with both lung cancer and tuberculosis underwent [18F]-FDG and Al[18F]-NOTA-FAPI-04 positron emission tomography/computed tomography (PET/CT) to determine staging. Additionally, a literature review was conducted to discuss the potential clinical applications of FAPI PET/CT. We reported a 70-year-old man with newly diagnosed lung squamous cell carcinoma underwent [18F]-FDG and Al[18F]-NOTA-FAPI-04 PET/CT to determine staging. The avid uptake of [18F]-FDG in old pulmonary TB and the right hilar inflammatory lymph nodes (<1 cm) were not found on Al [18F]-NOTA-FAPI-04 PET/CT. After 2 months of follow-up, the small lymph node was finally confirmed to be inflammatory.

Conclusion

Al[18F]-NOTA-FAPI-04 PET/CT may perform better in distinguishing TB from malignancy and may offer greater specificity than [18F]-FDG PET/CT for the diagnosis inflammatory lymph nodes.

Comparative Study of Dimeric Fibroblast Activation Protein-Targeting Radioligands Labeled with Fluorine-18, Copper-64, and Gallium-68

Fibroblast activation protein inhibitors (FAPIs) labeled with gallium-68 and lutetium-177 show potential for use in the diagnosis and treatment of various cancers expressing FAP. However, 177Lu-labeled FAPIs often exhibit short tumor retention time, limiting their therapeutic applications. To improve tumor retention, we synthesized three radiolabeled dimeric FAPIs, [18F]1, [64Cu]2, and [68Ga]3. These were prepared by chelating Al[18F]F to 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA)-l-glutamic acid (E)-(FAPI)2 and copper-64 or gallium-68 to 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-E-(FAPI)2. NOTA-E-(FAPI)2 and DOTA-E-(FAPI)2 showed higher binding affinities for FAP compared with that of FAPI-04 (IC50 = 0.47 and 0.16 nM vs 0.89 nM, respectively). All radioligands were synthesized in high decay-corrected radiochemical yields (59-96%) and were stable in fetal bovine serum and phosphate-buffered saline. The more hydrophilic radioligand, [68Ga]3, was selected for cellular uptake studies, which confirmed FAP-specific uptake. Positron emission tomography imaging and ex vivo biodistribution studies in U87MG tumor-bearing mice revealed high tumor uptake of all three radioligands, with significant blocking observed after preinjection of FAPI-04. [64Cu]2 and [68Ga]3 exhibited favorable in vivo pharmacokinetics compared to those of [18F]1. Notably, [68Ga]3 showed lower normal organ uptake than did the other two radioligands, and moreover, it exhibited higher, more prolonged tumor uptake than its monomeric counterpart [68Ga]Ga-FAPI-04 over a 3 h period, suggesting its potential as a promising FAP-specific theranostic radioligand.

Preclinical Evaluation of 68Ga/177Lu-Labeled FAP-Targeted Peptide for Tumor Radiopharmaceutical Imaging and Therapy

Fibroblast activation protein (FAP) has been considered a promising target for tumor imaging and therapy. This study designed a novel peptide, FAP-HXN, specifically targeting FAP and exhibiting significant potential as a radionuclide-labeled theranostic agent. Preclinical studies were conducted to evaluate the potency, selectivity, and efficacy of FAP-HXN. Methods: FAP-HXN was synthesized and characterized for selectivity and specificity toward FAP. Cellular uptake of the radiolabeled FAP-HXN in human embryonic kidney (HEK)-293-FAP cells with high expressions of FAP was evaluated. The diagnostic and therapeutic potential of 68Ga- and 177Lu-labeled radioligands was evaluated in HEK-293-FAP tumor-bearing mice compared with the FAP-targeting peptide FAP-2286. Results: FAP-HXN demonstrated high binding ability to human and mouse sources of FAP. Moreover, the in vivo studies confirmed the high affinity and specificity of radiolabeled FAP-HXN. Small-animal PET imaging demonstrated that [68Ga]Ga-FAP-HXN had continuous tumor uptake in FAP-positive tumors after administration compared with [68Ga]Ga-FAP-2286. In the therapeutic experiments, [177Lu]Lu-FAP-HXN showed significant antitumor activity in HEK-293-FAP xenografts at well-tolerated doses, which also exhibited longer tumor retention and better tumor growth inhibition compared with [177Lu]Lu-FAP-2286. Conclusion: The preclinical studies revealed that radiolabeled FAP-HXN had high tumor uptake, prolonged retention, and significant anticancer efficacy in HEK-293-FAP xenografts. FAP-HXN shows promising potential as a novel theranostic radioligand for FAP-positive tumors.

Head-to-Head Comparison of 68Ga-FAPI-04 and 68Ga-DOTA-TATE PET/CT in Recurrent Medullary Thyroid Cancer

PURPOSE

We aimed to compare the diagnostic performance of 68Ga-FAPI-04 (FAPI) in comparison to 68Ga-DOTATATE (SSTR) PET/CT for patients presenting with recurrent medullary thyroid carcinoma (MTC).

PATIENTS AND METHODS

Sixteen MTC patients with elevated calcitonin levels (>150 pg/mL) underwent FAPI and SSTR PET/CT. Two nuclear medicine physicians evaluated all images, categorizing lesions into locoregional metastases, mediastinal lymph nodes (LNs), liver, and bone metastases. SUVmax and tumor-to-background ratio were recorded. PET modalities were compared using the McNemar test. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of FAPI and SSTR PET were calculated.

RESULTS

The cohort comprised 16 patients (50% female; mean age 50 ± 17 years). Median calcitonin and CEA levels were 6234 pg/mL and 17.3 ng/mL, respectively. In patient-based analysis, SSTR exhibited higher diagnostic sensitivity compared with FAPI (88% vs 81%), resulting a statistically significant difference (P = 0.004). Mean SUVmax and tumor-to-background ratio values were 10.3 and 5.35 for FAPI, and 9.7 and 11.9 for SSTR PET, respectively. In lesion-based analyses, FAPI demonstrated higher accuracy than SSTR for cervical LNs (91.9% vs 50%), mediastinal LNs (94.9% vs 54.4%), and liver metastases (57.4% vs 7.3%), respectively. Notably, 31% of patients (n = 5) with FAP-expressing liver lesions showed no uptake on SSTR imaging. MRI confirmed liver metastases in 3 of these patients; however, 2 FAP-expressing lesions were confirmed as hemangiomas. False-positive findings of DOTA primarily included reactive LNs and bone hemangiomas.

CONCLUSIONS

FAPI PET presents promising outcomes in detecting metastases in recurrent MTC patients. Although its diagnostic performance matches SSTR on a per-patient basis, FAPI PET exhibits superior sensitivity and accuracy in lesion-based analyses, notably for liver and bone metastases.

18F-FAPI-42 PET/CT and 18F-FDG PET/CT in Patients with Malignant Digestive System Neoplasms: A Head-to-Head Comparative Study

PURPOSE

Radionuclide-labeled fibroblast activation protein inhibitor (FAPI) is an emerging tumor tracer. We sought to assess the uptake and diagnostic performance of 18F-FAPI-42 PET/CT compared with simultaneous 2-deoxy-2[18F]fluoro-D-glucose (18F-FDG) PET/CT in primary and metastatic lesions in patients with malignant digestive system neoplasms and to determine the potential clinical benefit.

PROCEDURES

Forty-two patients (men = 30, women = 12, mean age = 56.71 ± 13.26 years) who underwent 18F-FDG PET/CT and 18F-FAPI-42 PET/CT simultaneously for diagnosis, staging, and restaging were enrolled. Quantitative data, including standardized uptake value (SUV), tumor-to-liver ratio (TLR), and tumor-to-blood pool ratio (TBR), were analyzed. Two independent readers performed a visual assessment of lesion number and location on PET/CT images. Interobserver agreement between two examinations was calculated using Cohen's kappa (κ).

RESULTS

Primary tumor locations included the liver (n = 20), stomach (n = 9), pancreas (n = 5), and intestine (n = 10). More intense 18F-FAPI-42 uptake and higher tumor-to-background contrast were detected in most primary and metastatic lesions compared with 18F-FDG, contributing to improved diagnostic accuracy ranging from 95.24% to 100%. Moreover, additional lesions showing 18F-FAPI-42 uptake in primary, locoregional and distant metastatic lesions were visualized, especially in multiple liver and peritoneal metastases. Patient-based interobserver agreement varied from moderate to strong, with suboptimal outcomes observed in primary tumors (κ = 0.441, P = 0.01) and preferable results derived from metastatic liver and bone lesions (κ = 1 and 0.896, both P < 0.01). 18F-FAPI-42 PET/CT resulted in modified treatment strategies for 40.48% (17/42) of patients, while 18F-FDG PET/CT led to altered therapeutic regimens in only 4.8% (2/42) of patients.

CONCLUSIONS

In selected patients with malignant digestive system neoplasms, our study shows that 18F-FAPI-42 PET/CT is a promising alternative for assessing primary tumors and metastases and aiding staging, restaging, and decision-making, with higher uptake and better lesion visualization compared with 18F-FDG. Additionally, it may shed light into the treatment selection and response assessment for FAP-targeted therapy or immunotherapy.

Design, preclinical evaluation, and first-in-human PET study of [68Ga]Ga-PSFA-01: a PSMA/FAP heterobivalent tracer

PURPOSE

Prostate cancer (PCa), characterized by tumor heterogeneity, may exhibit low or absent prostate-specific membrane antigen (PSMA) expression in cancerous lesions, limiting the detection sensitivity of monospecific probes. Given that fibroblast activation protein (FAP) is frequently overexpressed in the tumor microenvironment (TME), we developed a PSMA/FAP dual-targeting tracer to address this limitation.

METHODS

The precursor (PSFA-01) was synthesized by coupling a quinolone-based FAP-targeting scaffold and EuK with HBED-CC via amide bonds. The dual-receptor-binding affinity and cell uptake of PSFA-01 and [natGa]Ga-PSFA-01 was evaluated in vitro. Micro-PET/CT imaging was performed on 22Rv1 and U87MG tumor-bearing mice. The feasibility of [68Ga]Ga-PSFA-01 PET/CT in a clinical setting was evaluated in a metastatic prostate cancer patient, and the results were compared with those of [68Ga]Ga-FAPI-04 and [68Ga]Ga-PSMA-11 PET/CT.

RESULTS

PSFA-01 and [natGa]Ga-PSFA-01 showed high affinity for both FAP and PSMA proteins (Ki = 0.14-1.02 nM). On micro-PET/CT imaging, the 22Rv1 tumor uptake of [68Ga]Ga-PSFA-01 (SUVmax = 3.89 ± 0.47) was higher than that of [68Ga]Ga-PSMA-11 (SUVmax = 2.96 ± 0.48). The U87MG tumor uptake of [68Ga]Ga-PSFA-01 was significantly higher (SUVmax = 7.29 ± 1.13) than [68Ga]Ga-FAPI-04 (SUVmax = 0.28 ± 0.12), showing tumor to muscle ratio as 12.68 ± 1.93 at 1 h p.i. On clinical trial, the primary tumor and metastatic lesions were distinctly identified by [68Ga]Ga-PSFA-01 (21 lesions), demonstrating superior performance compared to [68Ga]Ga-FAPI-04 (3 lesions) and [68Ga]Ga-PSMA-11 (13 lesions) in terms of lesion count and specificity.

CONCLUSIONS

[68Ga]Ga-PSFA-01 exhibited satisfactory PSMA and FAP dual-receptor-targeting properties both in vitro and in vivo. This study highlights the clinical feasibility of [68Ga]Ga-PSFA-01 PET/CT for detecting metastatic tumors of prostate cancer more sensitively compared to monomeric [68Ga]Ga-PSMA-11 and [68Ga]Ga-FAPI-04, which also suggests that a PSMA/FAP dual-targeted radionuclide therapy could potentially overcome challenges related to tumor heterogeneity and insufficient PSMA expression in PCa.

TRIAL REGISTRATION

Clinical trial registry NCT06387381, Registered 1 May 2024.

Comparison of 68Ga-FAPI PET CT/MRI and 18F-FDG PET/CT in metastatic lesions of gynecological cancers: a systematic review and head-to-head meta-analysis

Background68Ga-labled fibroblast activating protein inhibitor (68Ga-FAPI) represents a new and exciting positron emission tomography-computed tomography/magnetic resonance (PET-CT/MR) radiotracer.PurposeTo compare the diagnostic efficacy of 68Ga-FAPI PET CT/MR and 18F-fluorodeoxyglucose (18F-FDG) PET/CT in metastatic lesions of gynecological cancers (GCs).Material and MethodsThe PubMed, Embase, and Web of Science databases were thoroughly investigated from inception until 22 December 2023. A head-to-head contrast between 18F-FDG PET/CT as well as 68Ga-FAPI PET CT/MR for the assessment of GCs was presented by the included studies. A random variable model was employed to examine the sensitivity in detection of lymph node (LN) and peritoneal metastases (PM).ResultsThe pooled sensitivity for 68Ga-FAPI PET CT/MR and 18F-FDG PET/CT in lymph node metastases (LNM) of GC were 0.98 (95% confidence interval [CI] = 0.86-1) and 0.85 (95% CI = 0.65-0.98), respectively, while the results about peritoneal metastases in ovarian cancer were 0.98 (95% CI = 0.93-1) and 0.71 (95% CI = 0.55-0.86). Compared with 18F-FDG PET/CT, 68Ga-FAPI PET CT/MR exhibited a better sensitivity in peritoneal involvement of ovarian cancer with a relative risk of 0.24 (95% CI = 0.09-0.40) and P = 0.002.Conclusion68Ga-FAPI PET CT/MR displayed a superior sensitivity over 18F-FDG PET/CT in detecting metastatic lesions of ovarian cancer. However, there was insufficient evidence to favor the superiority of 68Ga-FAPI PET CT/MR in LNM of CC. Further studies are needed for evaluating primary and metastatic lesions of 68Ga-FAPI PET CT/MR in different GC.

FAP-targeted PET/CT imaging in patients with breast cancer from a prospective bi-center study: insights into diagnosis and clinic management

PURPOSE

To evaluate the diagnostic accuracy and clinical impact of fibroblast activation protein (FAP)-targeted PET/CT imaging in primary and metastatic breast cancer and compare the results with those of standard-of-care imaging (SCI) and [18F]FDG PET/CT.

METHODS

We prospectively analyzed patients with diagnosed or suspected breast cancer who underwent concomitant FAP-targeted PET/CT (radiotracers including either [68Ga]Ga-FAPI-46 or [18F]FAPI-42) and [18F]FDG PET/CT scans from June 2020 to January 2024 at two medical centers. Breast ultrasound (US) imaging was performed in all treatment-naïve patients as SCI. The SUVmax, tumor-to-background ratio (TBR), lesion detection rate, and tumor-node-metastasis (TNM) classifications between FAP-targeted and [18F]FDG PET/CT were evaluated and compared.

RESULTS

Sixty-one female patients (median age, 52 y; range, 28-82 y) were included. Among them, 23 patients underwent evaluation for a definitive diagnosis of suspected breast lesions, 15 underwent initial staging, and 23 were evaluated for the detection of recurrence. The sensitivities of breast US, [18F]FDG, and FAP-targeted PET/CT for detecting primary breast tumors were 82%, 79%, and 100%, respectively. Regarding the diagnosis of recurrent/metastatic lesions, the lesion-based detection rate of FAP-targeted PET/CT was significantly higher than that of [18F]FDG, which included local and regional recurrence, neck lymph node (LN), abdomen LN, bone, and liver metastases. Compared with [18F]FDG PET/CT, FAP-targeted PET/CT altered thirteen patients' TNM staging/restaging (13/59, 22%) and nine patients' clinical management (9/59, 15%). Compared to SCI, FAPI changed fourteen patients' TNM staging/re-staging (14/59, 24%) and eleven patients' therapeutic regimens(11/59, 19%). There was no significant association between FAPI-derived SUVmax and receptor status/histologic type in both primary and metastatic lesions.

CONCLUSION

FAP-targeted PET/CT was superior to [18F]FDG in diagnosing primary and metastatic breast cancer, with higher radiotracer uptake and TBR, especially in the detection of primary/recurrent tumors, abdominal LN metastases, liver, and bone metastases. FAP-targeted PET/CT is superior to [18F]FDG and SCI in TNM staging and may improve tumor staging, recurrence detection, and implementation of necessary treatment modifications.

Current and Emerging Radiotracers and Technologies for Detection of Advanced Differentiated Thyroid Cancer: A Narrative Review

Differentiated thyroid cancer (DTC), which includes papillary and follicular thyroid cancers, differs significantly in pathology compared to other thyroid malignancies such as medullary thyroid cancer (MTC), anaplastic thyroid cancer (ATC), and Hurthle cell carcinoma [...].

Prognostic and diagnostic value of [18F]FDG, 11C-acetate, and [68Ga]Ga-FAPI-04 PET/CT for hepatocellular carcinoma

OBJECTIVES

To assess the prognostic value of Fluorine 18-labeled fluorodeoxyglucose [18F]FDG, gallium 68-labeled fibroblast-activation protein inhibitor-04 [68Ga]Ga-FAPI-04, 11C-acetate in hepatocellular carcinoma (HCC) and evaluate the potential usefulness and advantages of different combinations for accurate diagnosis.

MATERIALS AND METHODS

Thirty-six patients with suspected hepatic masses were prospectively enrolled from May 2021 to September 2022 and underwent [18F]FDG, [68Ga]Ga-FAPI-04, and 11C-acetate PET/CT scans before surgery. PET/CT results and histopathologic examinations were independently interpreted by two radiologists and pathologists, respectively. Kaplan-Meier overall survival curves were calculated and the sensitivity among [18F]FDG, 11C-acetate, [68Ga]Ga-FAPI-04, and different combinations were compared.

RESULTS

Of the 36 included patients (mean age, 59 years ± 10 (standard deviation)), 29 were diagnosed with HCC, four with non-HCC malignant tumors, and three with benign tumors. Patients with HCC lesions negative for 11C-acetate or [68Ga]Ga-FAPI-04 exhibited poorer overall survival. Out of 36 patients, 44 HCC lesions were detected. The dual-tracer [68Ga]Ga-FAPI-04/11C-acetate exhibited the highest sensitivity (39 of 44 lesions (88.6%)) among all schemes. HCC lesions with higher histological grade and microvascular invasion (MVI) showed higher maximum standardized uptake value (SUVmax) and tumor-to-background ratio (TBR) of [18F]FDG, but no evidence of significant differences was found in [68Ga]Ga-FAPI-04 and 11C-acetate PET/CT. Higher expression of fibroblast activation protein (FAP) showed higher uptake of [68Ga]Ga-FAPI-04 and [18F]FDG.

CONCLUSION

[68Ga]Ga-FAPI-04 and 11C-acetate PET/CT exhibited good predictive value for HCC patients, with their combination showing the highest sensitivity for HCC detection, suggesting potential for improved diagnostic protocols.

KEY POINTS

Question What are the prognostic and diagnostic values of PET/CT tracers, including [18F]FDG, [68Ga]FAPI-04, and 11C-acetate? Findings Hepatocellular carcinoma, with differing findings across [18F]FDG, [68Ga]GaFAPI-04, and 11C-acetate PET/CT, showed varied prognoses; [68Ga]GaFAPI-04 and 11C-acetate combined offered the highest detection sensitivity. Clinical relevance Evaluating the prognostic value and diagnostic efficacy of different tracer combinations in patients with hepatocellular carcinoma helps to guide the optimal selection of tracers in clinical practice.

First Clinical Experience of 68Ga-FAPI PET/CT in Tertiary Cancer Center: Identifying Pearls and Pitfalls

Background/Objectives: Over the past four years, 68Ga-fibroblast activation protein inhibitor (FAPI) positron emission tomography/computed tomography (PET/CT) has been established at a tertiary cancer care facility in Jordan. This retrospective study aims to explore tracer uptake metrics across various epithelial neoplasms, identify diagnostic pitfalls associated with 68Ga-FAPI PET/CT, and evaluate the influence of 68Ga-FAPI PET/CT staging results on changes in therapeutic intent compared to gold standard molecular imaging modalities. Methods: A total of 48 patients with biopsy-confirmed solid tumors underwent 77 68Ga-FAPI PET/CT examinations for molecular imaging assessment, encompassing neoplasms originating from the gastrointestinal tract, head and neck, hepatobiliary system, pancreas, breast, and lung. Results: Notably, pancreaticobiliary tumors exhibited the highest tracer uptake, with mean maximum standardized uptake values (SUVmax) and tumor-to-background ratios (TBR) surpassing 10. A comparative sub-analysis of 68Ga-FAPI PET metrics in 20 treatment-naïve patients revealed a significant correlation between 68Ga-FAPI uptake metrics and tumor grade (Spearman's rho 0.83; p = 0.00001). Importantly, the results from 68Ga-FAPI PET/CT influenced treatment decisions in 35.5% of the cases, primarily resulting in an escalation of management plans. A total of 220 diagnostic challenges were identified across 88.3% of the scans, predominantly within the musculoskeletal system, attributed to degenerative changes (99 observations). Conclusions: This comprehensive analysis highlights the potential significance of 68Ga-FAPI PET/CT in oncological imaging and treatment strategy, while also emphasizing the necessity for meticulous interpretation to mitigate diagnostic challenges.

Radiopharmaceuticals and their applications in medicine

Radiopharmaceuticals involve the local delivery of radionuclides to targeted lesions for the diagnosis and treatment of multiple diseases. Radiopharmaceutical therapy, which directly causes systematic and irreparable damage to targeted cells, has attracted increasing attention in the treatment of refractory diseases that are not sensitive to current therapies. As the Food and Drug Administration (FDA) approvals of [177Lu]Lu-DOTA-TATE, [177Lu]Lu-PSMA-617 and their complementary diagnostic agents, namely, [68Ga]Ga-DOTA-TATE and [68Ga]Ga-PSMA-11, targeted radiopharmaceutical-based theranostics (radiotheranostics) are being increasingly implemented in clinical practice in oncology, which lead to a new era of radiopharmaceuticals. The new generation of radiopharmaceuticals utilizes a targeting vector to achieve the accurate delivery of radionuclides to lesions and avoid off-target deposition, making it possible to improve the efficiency and biosafety of tumour diagnosis and therapy. Numerous studies have focused on developing novel radiopharmaceuticals targeting a broader range of disease targets, demonstrating remarkable in vivo performance. These include high tumor uptake, prolonged retention time, and favorable pharmacokinetic properties that align with clinical standards. While radiotheranostics have been widely applied in tumor diagnosis and therapy, their applications are now expanding to neurodegenerative diseases, cardiovascular diseases, and inflammation. Furthermore, radiotheranostic-empowered precision medicine is revolutionizing the cancer treatment paradigm. Diagnostic radiopharmaceuticals play a pivotal role in patient stratification and treatment planning, leading to improved therapeutic outcomes in targeted radionuclide therapy. This review offers a comprehensive overview of the evolution of radiopharmaceuticals, including both FDA-approved and clinically investigated agents, and explores the mechanisms of cell death induced by radiopharmaceuticals. It emphasizes the significance and future prospects of theranostic-based radiopharmaceuticals in advancing precision medicine.

68Ga-DOTA-FAPI-04 and 18F-FDG PET/CT: a head-to-head comparison for peritoneal carcinomatosis diagnostic accuracy

PURPOSE

The study aimed to compare the diagnostic accuracy of 68Ga-DOTA-FAPI-04 (68Ga-FAPI) and 18F-FDG PET/CT for peritoneal carcinomatosis (PC) in patients with various types of cancer.

METHODS

The study enrolled 113 patients with suspected peritoneal malignancy, each of whom underwent 68Ga-FAPI and 18F-FDG PET/CT scans. Lesions in all patients were confirmed through pathology or radiological follow-up. The evaluation and comparison of diagnostic performance, visual scores, maximum standardized uptake value (SUVmax), mean tumor-to-background ratio (TBR), and the peritoneal cancer index (PCI) score were conducted.

RESULTS

Compared to 18F-FDG, 68Ga-FAPI PET/CT presented higher sensitivity, negative predictive value, and accuracy for detecting PC on a patient-level (100% vs. 93.2%, 100% vs. 22.22% and 93.81% vs. 86.73%, respectively). Semi-quantitative evaluation revealed that 68Ga-FAPI PET/CT had significantly higher SUVmax and TBR for PC [(6.06 ± 3.04 vs. 4.82 ± 2.75, P = 0.001) and (8.50 ± 5.01 vs. 2.92 ± 1.67, P < 0.001)]. The PCI-FAPI score for PC was higher than the PCI-FDG score (11.28 ± 7.10 vs. 5.69 ± 5.15, P < 0.001).

CONCLUSIONS

68Ga-FAPI has demonstrated superior diagnostic accuracy compared to 18F-FDG PET/CT in detecting PC with various types of cancer, particularly gastric cancer. Additionally, 68Ga-FAPI has shown significantly higher uptake and PCI score in PC compared to 18F-FDG, indicating its potential importance in clinical.

Uptake of 68 Ga-DOTA-FAPI-04 in a Case of Gynecomastia

ABSTRACT

Herein, we report a case of a man with malignant melanoma exhibiting thickened right breast with increased tracer uptake on 68 Ga-DOTA-FAPI-04 PET/CT. Subsequent ultrasound confirmed there was no sign of malignancy and consistent with benign gynecomastia.

Brain Tumor Assessment: Integrating PET/Computed Tomography and MR Imaging Modalities

While MR imaging is the main imaging modality to assess brain tumors, PET imaging has a specific role. Among the many tracers that have been proposed and are still being developed, 2-[18F]fluoro-2-deoxy-d-glucose ([18F]FDG) and O-(2-[18F]-fluoroethyl)-l-tyrosine ([18F]FET) PET remain the most solidly established in the clinics. In particular, [18F]FET has gained increased acceptance due to its higher sensitivity. In this paper, we present an overview of the current clinical status of brain tumor imaging, with emphasis on PET imaging.

Role of molecular imaging in prognosis, diagnosis, and treatment of gastrointestinal cancers: An update on new therapeutic methods

One of the leading causes of cancer-related death is gastrointestinal cancer, which has a significant morbidity and mortality rate. Although preoperative risk assessment is essential for directing patient care, its biological behavior cannot be accurately predicted by conventional imaging investigations. Potential pathophysiological information in anatomical imaging that cannot be visually identified can now be converted into high-dimensional quantitative image features thanks to the developing discipline of molecular imaging. In order to enable molecular tissue profile in vivo, molecular imaging has most recently been utilized to phenotype the expression of single receptors and targets of biological therapy. It is expected that molecular imaging will become increasingly important in the near future, driven by the expanding range of biological therapies for cancer. With this live molecular fingerprinting, molecular imaging can be utilized to drive expression-tailored customized therapy. The technical aspects of molecular imaging are first briefly discussed in this review, followed by an examination of the most recent research on the diagnosis, prognosis, and potential future clinical methods of molecular imaging for GI tract malignancies.

In Vivo Detection of Lymph Nodes Metastasis of ESCC Using CXCR4-Targeted Tracer [64Cu]Cu-NOTA-CP01

PURPOSE

Esophageal squamous cell carcinoma (ESCC) frequently exhibits skip metastasis to lymph nodes; however, non-invasive imaging techniques capable of directly visualizing metastatic lymph nodes (MLN) are still lacking. Although biopsy is the clinical standard method, it is invasive and poses risks to patient health. This study aims to detect MLN in an intralymphatic tumor metastasis model of ESCC using the CXCR4-targeted tracer [64Cu]Cu-NOTA-CP01.

PROCEDURES

The CXCR4 expression in ESCC cell lines was assessed using Western blot and immunofluorescence. An intralymphatic tumor metastasis model was established and monitored using bioluminescence imaging (BLI). Small animal PET studies and biodistribution studies were performed to evaluate the specificity of [64Cu]Cu-NOTA-CP01 for MLN. Histopathology evaluation was employed to check for the presence of metastatic tumor cells and to assess CXCR4 expression levels in the metastatic lymph nodes.

RESULTS

The intralymphatic tumor metastasis model was successfully established using the EC109/Luc cell line, which exhibited high CXCR4 expression, as verified by BLI. PET/CT imaging showed that the MLN uptakes in the baseline group were significantly inhibited in the blocking group. The ratios of MLN/muscle and MLN/blood were also significantly higher in the baseline group than in the blocking group. Ex vivo PET/CT imaging of MLN corroborated the in vivo data. Biodistribution studies further supported the PET imaging studies, showing rapid clearance of the tracer from the blood and major organs, with significantly higher MLN/muscle and MLN/blood ratios in the baseline group compared to the blocking group. Histopathological staining verified positive CXCR4 expression in these lymph nodes containing metastatic tumor cells.

CONCLUSIONS

Targeting CXCR4 with [64Cu]Cu-NOTA-CP01 for PET imaging of lymph nodes metastasis represents a promising approach that warrants further investigation. These findings have the potential to enhance diagnostic and therapeutic strategies for individuals with lymph nodes metastasis of ESCC.

Performance of fibroblast activating protein inhibitor PET imaging for pancreatic neoplasms assessment: a systematic review and meta-analysis

BACKGROUND

Recent studies have shown the potential of fibroblast activating protein inhibitor (FAPI) PET imaging for pancreatic cancer assessment.

PURPOSE

This article is dedicated to comparing the diagnostic efficacy of FAPI PET and [18F]fluorodeoxyglucose (FDG) PET in the evaluation of primary tumors, lymph nodes, and distant metastases in pancreatic cancer.

METHODS

In this review, we conducted a systematic search of studies published in PubMed and Web of Science databases up to September 18, 2023. All included studies used radionuclide labeled FAPI and FDG as PET diagnostic tracers to evaluate their applicability in patients with pancreatic cancer.

RESULTS

The FAPI PET imaging group showed significantly higher sensitivity in the detection of primary lesions (1.000, [95% CI: 0.999-1.000]), lymph node metastases (0.624 [95% CI: 0.391-0.834]) and distant metastatic (0.965 [95% CI: 0.804-1.000]) in pancreatic cancer compared to the FDG PET imaging group (0.889 [95% CI: 0.788-0.966], 0.373 [95% CI: 0.163-0.606] and 0.889 [95% CI: 0.689-0.999], respectively). Furthermore, the maximum standardized uptake value (SUVmax) in FAPI PET imaging is significantly higher than that in FDG imaging for primary lesions (mean difference (MD) = 7.51, 95% CI: 5.34-9.67).

CONCLUSION

Compared with [18F]FDG PET/CT, FAPI PET imaging showed higher sensitivity, SUVmax. This method can be effectively utilized for the evaluation of pancreatic cancer.

CLINICAL RELEVANCE STATEMENT

Fibroblast activating protein inhibitor PET may be a better alternative to [18F]FDG in evaluating primary pancreatic cancer, lymph node metastases, and distant metastases.

KEY POINTS

Fibroblast activating protein inhibitor (FAPI) PET is compared with FDG PET for evaluating pancreatic cancer. Multiple radiolabeled FAPI variants have shown promising results in the diagnosis of pancreatic cancer. FAPI PET imaging effectively helps clinicians diagnose and stage pancreatic cancer.

Towards a General Method for Using Cyclotron-Produced Ga68 to Manufacture Clinical and Research Ga68 Tracers

The success of multiple nuclear medicine radiotherapeutics in treating cancer requires an increased supply of companion diagnostic imaging agents radiolabeled with gallium-68. Cyclotron production addresses the need for access to gallium-68 and has been validated for use with commercially produced sterile kits. For novel research tracers undergoing translational studies (IND or RDRC), developing and purchasing sterile kits is time- and cost-prohibitive. An on-cassette labeling method with terminal filtration allows non-sterile kits to be fabricated in-house, simplifying workflow and allowing multiple PET imaging agents to be evaluated using the same kit (i.e., parts, reagents, and timelist) with minimal variation. Using modified GE gallium chloride cassettes, four diverse clinically relevant tracers (DOTA-TOC, FAPI-04, pentixafor, and PSMA-11) were radiolabeled with gallium-68 to evaluate the approach using DOTA and HBED-CC chelator types. The tracers were all formulated according to established FDA-approved formulations and sterile-filtered using a PVDF membrane. The automated procedure is robust, tolerating DOTA and HBED-CC chelators, and can be used to screen numerous gallium-68 agents for rapid translation to clinical use.

Impact of fat intake on [18F]AlF-NOTA-FAPI-04 uptake in normal abdominal organs

Purpose

[18F]AlF-NOTA-FAPI-04 demonstrates significant physiological uptake in the gallbladder and biliary tract system, representing a limitation of this positron emission tomography (PET) tracer. The aim of this study was to evaluate the impact of milk consumed prior to a PET/CT scan on [18F]AlF-NOTA-FAPI-04 uptake in normal abdominal organs.

Materials and methods

A total of 86 patients who underwent [18F]AlF-NOTA-FAPI-04 PET/CT imaging took part in this single-center retrospective clinical study at the Hunan Cancer Hospital between December 2020 and August 2021. Patients were divided into two groups according to their pre-PET scan diet: treated group, who consumed 250 mL of milk 10 ± 5 min after the tracer injection, while the control group was permitted no food intake subsequent to the radiotracer administration. The mean standardized uptake value (SUVmean) of gallbladder, liver, small intestine and pancreas were measured in 18F-FAPI and 18F-FDG PET/CT.

Results

There was a statistically significant difference in the 18F-FAPI uptake in the gallbladder between the treated group and the control group (p < 0.001). The average SUVmean in the treated group was 2.19 ± 2.01, which was significantly lower than the average SUVmean of 10.04 ± 9.66 in the control group. In the subgroup analysis of patients who underwent paired [18F]FDG and [18F]FAPI PET/CT scans, the 18F-FAPI uptake of liver and small intestine was significantly lower than the 18F-FDG uptake in both the treated group and the control group (p < 0.001).

Conclusion

This study suggests that milk consumption decreases physiological 18F-FAPI uptake in the gallbladder, potentially enhancing the diagnostic accuracy for gallbladder cancer.

Molecular Imaging Biomarkers for Early Cancer Detection: A Systematic Review of Emerging Technologies and Clinical Applications

BACKGROUND

Early cancer detection is crucial for improving patient outcomes. Molecular imaging biomarkers offer the potential for non-invasive, early-stage cancer diagnosis.

OBJECTIVES

To evaluate the effectiveness and accuracy of molecular imaging biomarkers for early cancer detection across various imaging modalities and cancer types.

METHODS

A comprehensive search of PubMed/MEDLINE, Embase, Web of Science, Cochrane Library, and Scopus was performed, covering the period from January 2010 to December 2023. Eligibility criteria included original research articles published in English on molecular imaging biomarkers for early cancer detection in humans. The risk of bias for included studies was evaluated using the QUADAS-2 tool. The findings were synthesized through narrative synthesis, with quantitative analysis conducted where applicable.

RESULTS

In total, 50 studies were included. Positron emission tomography (PET)-based biomarkers showed the highest sensitivity (mean: 89.5%, range: 82-96%) and specificity (mean: 91.2%, range: 85-100%). Novel tracers such as [68Ga]-PSMA for prostate cancer and [18F]-FES for breast cancer demonstrated promising outcomes. Optical imaging techniques showed high specificity in intraoperative settings.

CONCLUSIONS

Molecular imaging biomarkers show significant potential for improving early cancer detection. Integration into clinical practice could lead to earlier interventions and improved outcomes. Further research is needed to address standardization and cost-effectiveness.

Value of Semi-Quantitative Parameters of 68Ga-FAPI-04 PET/CT in Primary Malignant and Benign Diseases: A Comparison with 18F-FDG

Objectives: We compared the value of the semiquantitative parameters of 68Ga-labeled FAP inhibitor (68Ga-FAPI)-04 positron emission tomography/computed tomography (PET/CT) and 18F-fluorodeoxyglucose (18F-FDG) in diagnosing primary malignant and benign diseases. Materials and Methods: 18F-FDG and 68Ga-FAPI-04 PET/CT images of 80 patients were compared. Semiquantitative parameters, including maximum standardized uptake value (SUVmax), mean SUV (SUVmean), peak SUV (SUVpeak), peak SUV by lean body mass (SULpeak), metabolic tumor volume (or tumor volume of FAPI; FAPI-TV), and TLG (or total lesion activity of FAPI; FAPI-TLA), were automatically obtained using the IntelliSpace Portal image processing workstation with a threshold of 40% SUVmax. The liver blood pool was measured as the background, and the tumor-to-background ratio (TBRliver) was calculated. Results: In all malignant lesions, FAPI-TV and FAPI-TLA were higher in 68Ga-FAPI-04 PET/CT than in 18F-FDG. In the subgroup analysis, 68Ga-FAPI-04 had higher FAPI-TV and FAPI-TLA and lower SUVmax than 18F-FDG had in group A, including gynecological tumor, esophageal, and colorectal cancers. However, six semiquantitative parameters were higher in group B (the other malignant tumors). For the benign diseases, SUVmax, SUVmean, SUVpeak, and SULpeak were lower in 68Ga-FAPI-04 PET/CT than in 18F-FDG. 68Ga-FAPI-04 PET/CT showed a lower liver background and a higher TBRliver than 18F-FDG did. 68Ga-FAPI-04 PET/CT had higher accuracy, sensitivity, and specificity than 18F-FDG had. Conclusion: More accurate semiquantitative parameters and lower abdominal background in 68Ga-FAPI-04 PET/CT make it more competitive in the differential diagnosis of malignant and benign diseases than in 18F-FDG.

The diagnostic value of [18F]FAPI-42 PET/CT for pulmonary artery masses: comparison with [18F]FDG PET/CT

OBJECTIVES

To investigate the potential utility of [18F]fibroblast activation protein inhibitor (FAPI) positron emission tomography/computed tomography (PET/CT) for evaluating pulmonary artery (PA) masses, and compare it with [18F]fluorodeoxyglucose (FDG) PET/CT.

METHODS

Participants with clinically suspected PA malignancy were prospectively enrolled and underwent dual-tracer PET/CT ([18F]FAPI-42 and [18F]FDG) imaging. Visual analysis and semi-quantitative parameters were compared between the two types of radiotracers. The tissue specimen underwent immunohistochemical staining to verify FAP expression in the tissue.

RESULTS

Thirty-three patients (18 males/15 females; mean age 53.1 ± 15.4 years) were enrolled. All 21 patients with malignant PA masses were FDG-positive (100%), whereas 20 out of 21 patients were FAPI-positive (95.2%). All 12 patients with benign PA masses were both negative in FDG and FAPI PET. The mean maximum standardized uptake value (SUVmax) and target-to-background ratio (TBR) of FAPI and FDG in malignant PA masses were significantly higher than those of benign masses. Although there was no significant difference in SUVmax between FDG and FAPI in malignant PA masses (11.36 vs. 9.18, p = 0.175), the TBR (liver) and TBR (left ventricle) were more favorable for FAPI than for FDG (13.04 vs. 5.17, p < 0.001); (median: 7.75 vs. 2.75, p = 0.007). Immunohistochemical analysis (n = 16) validated that the level of FAP expression corresponded strongly to the uptake of FAPI in PET/CT scans (rs = 0.712, p = 0.002). For clinical management, FAPI PET found more metastatic lesions than FDG PET in 4 patients, with 2 patients upgrading and 1 patient changing treatment decisions.

CONCLUSIONS

FAPI PET/CT is feasible in the diagnosis of PA masses. Although not superior to FDG PET/CT, FAPI PET/CT showed better target-to-background contrast.

CLINICAL RELEVANCE STATEMENT

This study found that FAPI PET/CT is not superior to FDG PET/CT in diagnosing PA masses, but FAPI PET/CT displays better target-to-background contrast and more positive lesions, which may help improve disease management.

KEY POINTS

Pulmonary malignancies lack specificity in clinical manifestations, laboratory tests, and routine imaging examinations. FAPI PET/CT is not diagnostically better than FDG PET/CT but displays better target-to-background contrast and more positive lesions. Dual-tracer PET/CT ([18F]FAPI-42 and [18F]FDG) imaging improves clinical management of pulmonary artery masses.

[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.

Assessing the Value of 68Ga-FAPI PET/CT in Gastric Mucinous Adenocarcinoma or Signet Ring Cell Carcinoma

Purpose To investigate the clinical impact and prognostic value of gallium 68 (68Ga)-labeled fibroblast activation protein inhibitor (FAPI) PET/CT in gastric mucinous adenocarcinoma (MAC) and signet ring cell carcinoma (SRCC). Materials and Methods Eighty-six participants with newly diagnosed or recurrent gastric MAC or SRCC were prospectively enrolled from April 2021 to October 2021 and underwent both fluorine 18 (18F) fluorodeoxyglucose (FDG) PET/CT and 68Ga-FAPI PET/CT. The sensitivity, specificity, and accuracy of the two scans in primary and metastatic tumors were evaluated using the McNemar test. Changes of treatment strategies were recorded to compare the treatment management value of the two PET/CT scans. The maximum standardized uptake value (SUVmax) and peritoneal cancer index (PCI) were recorded for survival analysis. Progression-free survival (PFS) was defined as the time interval from the date of PET/CT scans to the date of disease progression. Results Eighty-six participants (median age, 62 years [IQR, 45-78 years]; 49 female) were evaluated. 68Ga-FAPI PET/CT showed higher diagnostic accuracy in detecting involved lymph nodes (87% [212 of 244] vs 71% [173 of 244], P < .001) and peritoneal metastases (96% [70 of 73] vs 55% [40 of 73], P < .001) than 18F-FDG PET/CT. Twenty-six participants (30% [26 of 86]) had treatment changes due to more accurate diagnosis with 68Ga-FAPI PET/CT. Additionally, the 68Ga-FAPI PCI was an independent predictor for PFS (hazard ratio, 6.9; 95% CI: 2.1, 23.1; P = .002). Conclusion 68Ga-FAPI PET/CT had higher accuracy in diagnosis of gastric MAC/SRCC compared with 18F-FDG PET/CT and demonstrated the potential to improve treatment strategies and predict prognosis. Keywords: PET/CT, Mucinous Adenocarcinoma, Signet Ring Cell Carcinoma, Oncology, Abdomen/GI, Molecular Imaging Supplemental material is available for this article. © RSNA, 2024.

Evaluation of 68Ga-FAPI PET/CT and 18F-FDG PET/CT for the diagnosis of recurrent colorectal cancers

Objective

The present study aimed to compare the diagnostic value of gallium-68-labeled fibroblast activation protein inhibitor positron emission tomography/computed tomography (68Ga-FAPI PET/CT) and fluorine-18-labeled fluorodeoxyglucose PET/CT (18F-FDG PET/CT) for detecting recurrent colorectal cancers (CRCs).

Materials and Methods

Fifty-six patients (age: 18-80 years, 31 men and 25 women) with suspected recurrent CRC were enrolled and underwent 18F-FDG PET/CT and 68Ga-FAPI PET/CT sequentially within 1 week. The maximum standard uptake value (SUVmax), tumor-to-background ratio (TBR), and diagnostic accuracy were estimated and compared between the two modalities by using Student's t-test. The Wilcoxon signed-rank test was used to compare peritoneal carcinoma index (PCI) scores between the two imaging modalities.

Results

68Ga-FAPI PET/CT showed higher sensitivity for detecting recurrence (93 % vs. 79 %); lymph node metastasis (89 % vs. 78 %), particularly peritoneal lymph node metastasis (92 % vs. 63 %); and metastatic implantation on the intestinal wall (100 % vs. 25 %) compared to 18F-FDG PET/CT. However, 68Ga-FAPI PET/CT showed lower sensitivity for detecting bone metastasis (67 % vs. 100 %). The mean SUVmax values of peritoneal metastases and metastatic implantation on the intestinal wall were 4.28 ± 2.70 and 7.58 ± 1.66 for 18F-FDG PET/CT and 5.66 ± 1.97 and 6.70 ± 0.25 for 68Ga-FAPI PET/CT, respectively. Furthermore, 68Ga-FAPI PET/CT showed significantly higher TBR for peritoneal metastatic lesions (4.22 ± 1.47 vs. 1.41 ± 0.89, p < 0.0001) and metastatic implantation on the intestinal wall (5.63 ± 1.24 vs. 2.20 ± 0.5, p = 0.02) compared to 18F-FDG PET/CT. For the same patient, 68Ga-FAPI PET/CT yielded a more accurate PCI score and a greater area under the curve value for the receiver operating characteristic curve (p < 0.01) than 18F-FDG PET/CT.

Conclusion

68Ga-FAPI PET/CT was superior to 18F-FDG PET/CT for detecting recurrence and peritoneal metastases. Hence, we propose the combination of these two modalities for better clinical diagnosis and management of patients with CRC.

68Ga/177Lu-Labeled Theranostic Pair for Targeting Fibroblast Activation Protein with Improved Tumor Uptake and Retention

Fibroblast activation protein (FAP) is specifically expressed on cancer-associated fibroblasts in over 90% of tumors and is considered a promising target for cancer theranostics. Here, we developed a novel tracer, DOTA-FAPT, and labeled it with gallium-68 and lutetium-177 as a theranostic pair. [68Ga]Ga/[177Lu]Lu-FAPT exhibited high stability and hydrophilicity, as well as strong affinity to the FAP target. Micro-PET/CT imaging revealed that [68Ga]Ga-FAPT exhibited significantly increased uptake in tumors and extended retention in A549-FAP and U87MG tumor xenografts as compared to [68Ga]Ga-FAPI-04, demonstrating favorable pharmacokinetic characteristics in vivo. Therapeutic studies showed that [177Lu]Lu-FAPT had higher tumor accumulation compared to [177Lu]Lu-FAPI-04, leading to stronger tumor growth inhibition. The first-in-human evaluation also revealed that [68Ga]Ga-FAPT has good in vivo distribution and superior diagnostic efficacy on primary and lymph node metastases in a patient with lung cancer. Our encouraging results suggest that 68Ga/177Lu-labeled DOTA-FAPT is a theranostic pair with broad application prospect.