Head-To-Head Comparison of 68Ga-FAPI PET/CT and FDG PET/CT for the Detection of Peritoneal Metastases: Systematic Review and Meta-Analysis

Diagnostic Performances of Radiolabeled FAPI PET/CT for Lymph Node Staging in Head and Neck Cancer Patients: Comparison With 18F-FDG PET/CT

OBJECTIVE

The purpose of the current study was to compare the diagnostic performances of radiolabeled FAPI and 18F-FDG PET/CT for the detection of lymph node (LN) metastasis in head and neck cancer (HNC) patients.

METHODS

The PubMed, Cochrane database, and EMBASE database, from the earliest available date of indexing through December 31, 2024, were searched for studies comparing diagnostic performances of radiolabeled FAPI and 18F-FDG PET/CT for the detection of metastatic LN in HNC patients. We estimated pooled sensitivities and specificities across studies.

RESULTS

Across 8 studies (14 results), the pooled sensitivity of FAPI PET/CT was 0.89 and the pooled specificity was 0.93. The pooled sensitivity of 18F-FDG PET/CT was 0.91 and the pooled specificity was 0.50. On patient-based analysis, the estimated sensitivity and specificity of FAPI were 0.96 and 0.96, and those of 18F-FDG were 0.95 and 0.34, respectively. On lesion-based analysis, the estimated sensitivity and specificity of FAPI were 0.84 and 0.94, and those of 18F-FDG were 0.86 and 0.78, respectively. On neck side-based analysis, the estimated sensitivity and specificity of FAPI were 0.88 and 0.79, and those of 18F-FDG were 0.91 and 0.29, respectively.

CONCLUSIONS

Radiolabeled FAPI showed a good diagnostic performance for the detection of metastatic LN in HNC patients. Also, 18F-FDG PET/CT revealed low specificity for LN staging in HNC patients. Future large multicenter research with more patients would be necessary to provide a more comprehensive overview of the usefulness of radiolabeled FAPI for LN staging in HNC patients.

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.

Comparative Evaluation of 68Ga-FAPI-04 PET for Initial N and M Staging in Gastric Cancer: A Study Against Histopathology and Contrast-Enhanced CT

PURPOSE

To evaluate the efficiency of 68Ga-FAPI-04 PET (PET/MRI or PET/CT) for N and M staging in gastric carcinoma and compare outcomes with histopathology and contrast-enhanced computed tomography (CECT).

PATIENTS AND METHODS

Patients with gastric carcinoma who had undergone 68Ga-FAPI-04 PET/MRI or PET/CT before treatment were retrospectively enrolled. Histopathology post lymphadenectomy was the gold standard for N staging, while histopathology and follow-up data were the reference for overall outcomes. The diagnostic efficiency of 68Ga-FAPI-04 PET for detecting regional lymph node involvement and distant metastases was compared to that of CECT.

RESULTS

Sixty-two patients were enrolled. In 18 patients who underwent 68Ga-FAPI-04 PET/MRI and lymphadenectomy, 532 lymph nodes were dissected. 68Ga-FAPI-04 PET/MRI showed similar sensitivity, specificity, and accuracy compared to CECT (28.3% vs. 23.2%, 99.8% vs. 99.3%, and 86.5% vs. 85.2%, all P > 0.05). Fifty-five patients had regional lymph node metastasis, 68Ga-FAPI-04 PET exhibited comparable diagnostic efficiency to CECT, with sensitivity of 83.6% versus 87.3%, specificity of 100% versus 85.7%, accuracy of 85.5% versus 87.1% (all P > 0.05). Excluding 3 patients with only abdominal CECT, 32 out of 59 patients had distant metastasis, with no significant differences in sensitivity, specificity, and accuracy between 68Ga-FAPI-04 PET and CECT based on patient (100% vs. 87.5%, 92.6% vs. 96.3%, and 96.6% vs. 91.5%, all P >0.05). Notably, 68Ga-FAPI-04 PET outperformed CECT in detecting peritoneal, distant lymph nodes, bone, liver, and ovarian metastases by visualizing more lesions or greater lesion extent.

CONCLUSIONS

68Ga-FAPI-04 PET exhibits comparable diagnostic performance to CECT for patient-based N staging and M staging of gastric cancer. However, it surpasses CECT in visualizing distant metastases.

Educational Review: Updates on Therapeutic Strategies for Gastric Cancer with Peritoneal Metastasis

Gastric cancer (GC) commonly presents in advanced stages with metastatic spread to the peritoneal cavity, and outcomes associated with gastric cancer with peritoneal metastasis (GCPM) continue to carry a dismal prognosis. Persistent challenges in the detection of peritoneal metastasis (PM) have resulted in a relative paucity of high-quality data to inform management decisions. Several consensus groups have published recommendations to guide management, including most recently the National Comprehensive Cancer Network guidelines, which now include cytoreductive surgery (CRS) with hyperthermic intraperitoneal chemotherapy (HIPEC) as a potential treatment modality in select patients with GCPM. Multiple clinical trials have investigated the use of CRS/HIPEC and other peritoneal-directed therapies, such as intraperitoneal chemotherapy (IPC) and pressurized intraperitoneal aerosolized chemotherapy (PIPAC). As high-volume centers work to incorporate such therapies into their practice, ongoing clinical trials are aimed at understanding their efficacy. Recent findings have improved understanding of the mechanisms and pathophysiology underlying GCPM while the discovery of novel targets offers potential for drug development and therapeutic strategies to overcome treatment resistance. This review highlights recent advancements and addresses the persistent challenges in managing GCPM while also offering a comprehensive summary of current guidelines and treatment strategies.

Review of Imaging Peritoneal Disease and Treatment

Peritoneal disease can be classified as either benign or malignant in nature. Malignant peritoneal disease can be further considered as either primary or secondary in origin. Primary peritoneal malignancy includes peritoneal mesothelioma, serous carcinoma, and desmoplastic small round cell tumour. Peritoneal carcinomatosis is the most commonly encountered secondary malignant peritoneal disease, typically of ovarian, gastric, colorectal, pancreatic, small bowel neuroendocrine, or breast origin. Others include peritoneal lymphomatosis and sarcomatosis. Benign peritoneal pathology may mimic malignant disease. Differentiating benign from malignant peritoneal pathology can be challenging, but is critical to guide appropriate care and avoid unnecessary intervention. Cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) offers potentially curative treatment for patients with peritoneal carcinomatosis, pseudomyxoma peritonei, and peritoneal mesothelioma. For such patients, the radiologist provides crucial pre-operative information highlighting sites of disease involvement, particularly for sites which are challenging to assess at laparotomy or laparoscopy, including the hepatic dome, subdiaphragmatic space and mesenteric root. The radiologist is also essential to identify potential contraindications to surgery, as well as interpreting normal post-operative appearances, complications and assessing for disease recurrence.

Fibroblast Activation Protein Inhibitor (FAPI)-Based Theranostics

Fibroblast activation protein (FAP) is a serine protease selectively expressed in cancer-associated fibroblasts (CAFs), fibrotic tissues, and areas of active tissue remodeling, making it an attractive target for diagnostic imaging across a spectrum of disease. FAP inhibitors (FAPIs) labeled with PET tracers have rapidly advanced as a novel imaging modality with broad clinical applications that offers several advantages, including rapid tumor accumulation, low background uptake, and high tumor-to-background ratios. In oncology, FAPI PET has demonstrated excellent performance in visualizing a wide range of malignancies, including those with low glycolytic activity, such as pancreatic cancer, cholangiocarcinoma, and certain sarcomas. Its high sensitivity and specificity for the stromal component enables improved tumor delineation, staging, and response assessment. Additionally, the potential to guide theranostic approaches, where the same tracer can be labeled with therapeutic radionuclides, positions FAPI as a key player in precision oncology. Beyond oncology, FAPI PET has shown promise in imaging conditions characterized by fibrotic and inflammatory processes. In the cardiovascular field, FAPI PET imaging is being investigated for its ability to detect myocardial fibrosis and active cardiac remodeling, crucial in conditions like heart failure, post-myocardial infarction remodeling, and hypertrophic cardiomyopathy. This review highlights the expanding clinical applications of FAPI-based PET imaging across oncology, inflammation, and cardiovascular disease. While the current data are promising, further large-scale studies and multicenter trials are essential to validate these findings and establish standardized protocols. The versatility and broad applicability of FAPI PET underscore its potential as a transformative tool in precision medicine.

Focal 68Ga-FAPI-04 Uptake in Endometriosis at the Rectouterine Pouch

Endometriosis is a benign condition characterized by chronic inflammation and fibrosis. We report the findings of endometriosis at the rectouterine pouch on 68Ga-FAPI-04 PET/CT scan in a 25-year-old woman. The finding was initially thought as peritoneal metastasis from her newly diagnosed gastric cancer. However, subsequent pathologic examination confirmed that it was endometriosis.

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.

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.

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.

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.

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.

Comparison of 68Ga-FAPI-04 and 18F-FDG PET/CT in diagnosing ovarian cancer

PURPOSE

This study assesses the diagnostic performance of 68Ga-FAPI-04 PET/CT compared to 18F-FDG PET/CT in primary, recurrent, and metastatic ovarian cancer.

METHODS

Seventy-nine ovarian cancer patients who performed 68Ga-FAPI-04 and 18F-FDG PET/CT were recruited. The target-to-background ratio (TBR), maximum standardized uptake value (SUVmax), the number of positive lesions, visual assessment, the peritoneal cancer index (PCI) score, staging/restaging, and treatment strategies were compared from the corresponding PET/CT. Additionally, we analyzed and contrasted the diagnostic efficacy in both scans.

RESULTS

Among all patients, 6 were assessed for initial assessment and 73 for recurrence and metastasis detection. For all lesions, 68Ga-FAPI-04 PET/CT demonstrated greater TBR than 18F-FDG PET/CT. 68Ga-FAPI-04 PET/CT demonstrated higher sensitivity for peritoneal metastases including patient-based and lesion-based analysis (95.00% vs. 83.33%, P = 0.065; 90.16% vs. 60.66%, P < 0.001) and a higher PCI score [median PCI: 6 (4, 12) vs. 4 (2, 8), P < 0.001]. According to the visual assessment, 68Ga-FAPI-04 PET revealed larger extent metastases in 55.93% (33/59) of the patients with peritoneal metastases. 68Ga-FAPI-04 was upstaged in 7 patients (8.86%, 7/79) and discrepancies in both scans caused treatment strategies to change in 11 patients (13.92%, 11/79).

CONCLUSION

68Ga-FAPI-04 PET/CT outperforms 18F-FDG PET/CT in identifying metastases and can be a potential supplement for managing ovarian cancer patients.

Head-to-head study of [18F]FAPI-04 PET/CT and [18F]FDG PET/CT for non-invasive assessment of liver cancer and its immunohistochemical markers

OBJECTIVE

To compare the performance of [18F]FDG and [18F]FAPI-04 in PET/CT evaluation for liver cancer lesions, with a further exploration of the associations between PET semiquantitative data and immunohistochemical markers to liver cancer.

METHODS

Patients with suspected malignant liver lesions (MLL) underwent [18F]FDG and [18F]FAPI-04 PET/CT scanning. Liver lesions were visually classified as positive or negative based on their uptake level exceeding that of adjacent normal liver tissue. SUVmax and tumor-to-background ratio (TBR) were recorded for semi-quantitative analysis. Sensitivity, specificity and accuracy of each tracer were determined using pathological findings as the gold standard. Furthermore, immunohistochemical analysis provided the molecular characteristics of all MLLs. Comprehensive analysis explored correlations between these molecular markers and PET semiquantitative parameters (SUVmax andTBR) to identify potential associations.

RESULTS

The study enrolled 44 patients, with 39 confirmed cases of MLL, comprising 28 hepatocellular carcinomas (HCC) and 11 intrahepatic cholangiocarcinomas (ICC). For MLL detection, [18F]FAPI-04 and [18F]FDG exhibited sensitivities of 84.6% (33/39) and 76.9% (30/39), specificitiesy of 60% (3/5) and 100%(5/5), and accuracy of 81.8% (36/44) and 79.5%(35/44). Across all liver lesions, [18F]FAPI-04 significantly surpassed [18F]FDG in SUVmax(10.54 ± 6.72 VS. 7.68 ± 6.79) and TBR(4.35 ± 3.78 Vs. 3.17 ± 3.05). Notably, [18F]FAPI-04 displayed markebly elevated SUVmax in benign liver lesions (BLLs) (P = 0.032), HCCs (P = 0.005), and ICCs (P = 0.011). Lesions with hepatocyte negativity (P = 0.023), CD34 negativity(P = 0.044), and high Ki67 expression (> 30%) (P = 0.001) had higher SUVmax on [18F]FAPI-04. Additionally, ARG-1-negative lesions demonstrated higher TBR on [18F]FAPI-04 than ARG-1-positive lesions(P = 0.018). No significant SUVmax/TBR differences were observed with [18F]FDG based on these markers. A linear relationship was identified between Ki67 scores and SUVmax of [18F]FAPI-04 (R = 0.603, P < 0.001).

CONCLUSION

[18F]FAPI-04 exhibits superior performance over [18F]FDG in PET/CT evaluation of liver cancer, characterized by increased sensitivity and SUVmax/TBR. Significant correlations with molecular markers, including Ki67, suggest [18F]FAPI-04's potential for characterizing liver cancer subtypes and assessing tumor proliferation. However, further research is required to validate these findings and their clinical significance.

TRIAL REGISTRATION

NCT05485792, Registered 01 August 2022.

Imaging of Peritoneal Surface Malignancies

Management of peritoneal surface malignancies is currently entrusted to a multimodality approach. Computed tomography (CT) scan remains the first imaging method despite the limitations in identifying small implants in critical regions. Magnetic resonance imaging is usually recommended for its performance in small implants, mesentery, and small bowel assessment. Positron emission tomography/CT plays an important role only in pseudomyxoma peritonei. Thus, becoming aware of the imaging strengths and drawbacks and having a multimodality imaging approach might be the best option for the patients.

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.

Radiomolecular Theranostics With Fibroblast-Activation-Protein Inhibitors and Peptides

The advancement of theranostics, which combines therapeutic and diagnostic capabilities in oncology, has significantly impacted cancer management. This review explores fibroblast activation protein (FAP) expression in the tumor microenvironment (TME) and its association with various malignancies, highlighting its potential as a theranostic marker for PET/CT imaging using FAP-targeted tracers and for FAP-targeted radiopharmaceutical therapy. We examine the development and clinical applications of FAP inhibitors (FAPIs) and peptides, providing insights into their diagnostic accuracy, initial therapeutic efficacy, and clinical impact across diverse cancer types, as well as the synthesis of novel FAP-targeted ligands. This review aims to showcase the promising outcomes and challenges in integrating FAP-targeted approaches into cancer management.

Staging laparoscopy in gastric cancer patients: From a Dutch nationwide Delphi consensus towards a standardized protocol

BACKGROUND

Staging laparoscopy is a common diagnostic tool in gastric cancer, but its performance varies widely. The aim of this study was to gain Dutch nationwide consensus regarding the indications for and execution of staging laparoscopy in patients with gastric cancer.

METHODS

All surgeons in the Netherlands specialized in gastric cancer surgery (n = 52) were asked to participate in a Delphi consensus study. The study involved an initial questionnaire with a 3-point Likert scale, an online consensus meeting, and a second questionnaire using a 2-point Likert scale (agree/disagree). Consensus was defined as 70% or more agreement among participants.

RESULTS

In total, 45 experts completed both questionnaires (87% response rate). Consensus was reached on the indication to perform staging laparoscopy in cT3-4 or cN + or diffuse-type gastric cancer, including Siewert type III oesophagogastric junctional cancer. The experts agreed that if preoperative scans suggest infiltration of surrounding organs (cT4), the tumour's resectability should explicitly be investigated. Consensus was also reached for a systematic peritoneal cavity inspection according to Sugarbaker's Peritoneal Cancer Index (PCI) score. All regions should be inspected routinely, although the omental bursa may be inspected on indication. Aspiration of ascites or peritoneal washing should be performed for cytology. The experts agreed that restaging laparoscopy should be performed before resection in case of progressive disease on preoperative imaging. Without progression, global inspection was considered sufficient.

CONCLUSIONS

The results of this Dutch nationwide Delphi consensus study exposed the variability of performing staging laparoscopy in patients with gastric cancer and provided the concept for a standardized protocol.

The yield of diagnostic laparoscopy with peritoneal lavage in gastric adenocarcinoma: A retrospective cohort study

INTRODUCTION

Diagnostic laparoscopy (DL) with peritoneal lavage has been adopted as a standard staging procedure for patients with gastric cancer (GC). Evaluation of the value of DL is important given ongoing improvements in diagnostic imaging and treatment. As contemporary data from European centres are sparse, this retrospective cohort study aimed to assess the yield of DL in patients with potentially curable gastric cancer, and to identify predictive factors for peritoneal metastases.

METHODS

Patients with adenocarcinoma of the stomach, treated between January 2016 and December 2018, were identified from institutional databases of two high volume European Upper-GI centres. Patients who underwent a DL with peritoneal lavage for potentially curable disease after clinical staging with imaging (cT1-4N0-3M0) were included. The primary outcome was the proportion of patients with a positive DL, defined as macroscopic metastatic disease, positive peritoneal cytology washings (PC+) or locally irresectable disease.

RESULTS

Some 80 of 327 included patients (24.5%) had a positive DL, excluding these patients from neoadjuvant treatment (66 of 327; 20.2%) and/or surgical resection (76 of 327; 23.2%). In 34 of 327 patients (10.3%), macroscopic metastatic disease was seen, with peritoneal deposits in 30 of these patients. Only 16 of 30 patients with peritoneal disease had positive cytology. Some 41 of 327 patients (12.5%) that underwent DL had PC+ in the absence of macroscopic metastases and five patients (1.5%) had an irresectable primary tumour. Diffuse type carcinoma had the highest risk of peritoneal dissemination, irrespective of cT and cN categories.

CONCLUSION

The diagnostic yield of staging laparoscopy is high, changing the management in approximately one quarter of patients. DL should be considered in patients with diffuse type carcinoma irrespective of cT and cN categories.

Imaging Evaluation of Peritoneal Metastasis: Current and Promising Techniques

Early diagnosis, accurate assessment, and localization of peritoneal metastasis (PM) are essential for the selection of appropriate treatments and surgical guidance. However, available imaging modalities (computed tomography [CT], conventional magnetic resonance imaging [MRI], and 18fluorodeoxyglucose positron emission tomography [PET]/CT) have limitations. The advent of new imaging techniques and novel molecular imaging agents have revealed molecular processes in the tumor microenvironment as an application for the early diagnosis and assessment of PM as well as real-time guided surgical resection, which has changed clinical management. In contrast to clinical imaging, which is purely qualitative and subjective for interpreting macroscopic structures, radiomics and artificial intelligence (AI) capitalize on high-dimensional numerical data from images that may reflect tumor pathophysiology. A predictive model can be used to predict the occurrence, recurrence, and prognosis of PM, thereby avoiding unnecessary exploratory surgeries. This review summarizes the role and status of different imaging techniques, especially new imaging strategies such as spectral photon-counting CT, fibroblast activation protein inhibitor (FAPI) PET/CT, near-infrared fluorescence imaging, and PET/MRI, for early diagnosis, assessment of surgical indications, and recurrence monitoring in patients with PM. The clinical applications, limitations, and solutions for fluorescence imaging, radiomics, and AI are also discussed.

Signet cell rectal carcinoma with prostatic involvement detected by FAPI-04 PET-MRI fusion

A 60-year-old male patient diagnosed with mucinous adenocarcinoma of lower third of rectum underwent abdominoperineal resection and permanent colostomy followed by adjuvant chemotherapy. Response evaluation with F-18 FDG PET-CT showed a complete metabolic response. After 6 months, CEA levels started increasing and clinically a recurrence was suspected. A restaging FDG PET-CT showed no obvious malignant disease. Patient presented again within a month with complaints of urinary retention and haematuria. CEA levels were further elevated, and Ga-68 FAPI-04 (FAPI) PET-CT was performed. FAPI PET-CT revealed prostatic and seminal vesicle disease involvement. Additionally, an MRI of pelvis was done and fused with FAPI PET for confirmation of prostatic involvement.

FAPI PET/CT Imaging-An Updated Review

Despite revolutionizing the field of oncological imaging, Positron Emission Tomography (PET) with [18F]Fluorodeoxyglucose (FDG) as its workhorse is limited by a lack of specificity and low sensitivity in certain tumor subtypes. Fibroblast activation protein (FAP), a type II transmembrane glycoprotein, is expressed by cancer-associated fibroblasts (CAFs) that form a major component of the tumor stroma. FAP holds the promise to be a pan-cancer target, owing to its selective over-expression in a vast majority of neoplasms, particularly epithelial cancers. Several radiolabeled FAP inhibitors (FAPI) have been developed for molecular imaging and potential theranostic applications. Preliminary data on FAPI PET/CT remains encouraging, with extensive multi-disciplinary clinical research currently underway. This review summarizes the existing literature on FAPI PET/CT imaging with an emphasis on diagnostic applications, comparison with FDG, pitfalls, and future directions.

Evaluation of the Diagnostic Accuracy of FAPI PET/CT in Oncologic Studies: Systematic Review and Metaanalysis

Fibroblast-activation protein is a promising target for oncologic molecular imaging. Studies show that fibroblast activation protein inhibitor (FAPI) radiotracers are accurate diagnostics with favorable tumor-to-background ratios across various cancers. Therefore, we performed a systematic review and metaanalysis to assess the diagnostic performance of FAPI PET/CT in comparison with [¹⁸F]FDG PET/CT, the most widely used radiotracer in oncology. Methods: We conducted a systematic search in MEDLINE, Embase, Scopus, PubMed, Cochrane Central Register of Controlled Trials, relevant trial registries, and bibliographies. The search consisted of combinations of terms for 3 topics: neoplasia, PET/CT, and FAPI. Two authors independently screened retrieved articles using predefined inclusion and exclusion criteria and extracted the data. Study quality was assessed using the criteria of QUADAS-2 (Quality Assessment of Diagnostic Accuracy Studies 2). For each study, the sensitivity, specificity, and 95% CIs were calculated to determine diagnostic accuracy for primary, nodal, and metastatic lesions. A random-effects metaanalysis was used for pooling the data, and heterogeneity was assessed (I² index). Results: Thirty-nine studies (1,259 patients) investigating the use of FAPI PET/CT were included. On a patient-based analysis, pooled sensitivity was 0.99 (95% CI, 0.97-1.0) for the detection of primary lesions. Pooled sensitivity for nodal and distant metastases was 0.91 (95% CI, 0.81-0.96) and 0.99 (95% CI, 0.96-1.0), respectively. On a paired analysis between FAPI and [¹⁸F]FDG PET/CT, FAPI had a higher sensitivity in the detection of primary, nodal, and metastatic lesions (all P < 0.001). The differences in sensitivities between FAPI and [¹⁸F]FDG were statistically significant. In terms of heterogeneity, analyses on primary lesions were moderately affected, distant metastatic lesions were highly affected, and the nodal metastatic analyses had negligible heterogeneity. Conclusion: The diagnostic performance of FAPI PET/CT is superior to that of [¹⁸F]FDG in the detection of primary, nodal, and distant metastases. However, further studies are needed to better evaluate its utility and indication in specific cancer types and clinical settings.

FMO family may serve as novel marker and potential therapeutic target for the peritoneal metastasis in gastric cancer

Objective

To explore the relationship between flavin-containing monooxygenases (FMOs) and peritoneal metastasis (PM) in gastric cancer (GC).

Materials and methods

TIMER 2.0 was used to perform pan-cancer analysis and assess the correlation between the expression of FMOs and cancers. A dataset from The Cancer Genome Atlas (TCGA) was used to analyze the correlation between FMOs and clinicopathological features of GC. PM is well established as the most common mode of metastasis in GC. To further analyze the correlation between FMOs and PM of GC, a dataset was obtained from the National Center for Biotechnology Information Gene Expression Omnibus (GEO) database. The results were validated by immunohistochemistry. The relationship between FMOs and PM of GC was explored, and a novel PM risk signature was constructed by least absolute shrinkage and selection operator (LASSO) regression analysis. The regression model's validity was tested by multisampling. A nomogram was established based on the model for predicting PM in GC patients. The mechanism of FMOs in GC patients presenting with PM was assessed by conducting Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses in TCGA and GEO datasets. Finally, the potential relationship between FMOs and immunotherapy was analyzed.

Results

The pan-cancer analysis in TCGA and GEO datasets showed that FMO1 was upregulated, while FMO2 and FMO4 were downregulated in GC. Moreover, FMO1 and FMO2 correlated positively with the T and N stage of GC in the TCGA dataset. FMO1 and FMO2 expression was a risk factor for GC (hazard ratio: 1.112 and 1.185). The overexpression of FMO1 was significantly correlated with worse disease-free-survival (DFS) and overall survival (OS). However, no relationship was found between FMO2 expression in GC and DFS and OS. PM was highly prevalent among GC patients and typically associated with a worse prognosis. FMO1 was highly expressed in GC with PM. FMO1 and FMO2 were positively correlated with PM in GC. We identified a 12-gene panel for predicting the PM risk signature by LASSO (Area Under Curve (AUC) = 0.948, 95%CI: 0.896-1.000). A 10-gene panel for PM prediction was identified (AUC = 0.932, 95%CI: 0.874-0.990), comprising FMO1 and FMO2. To establish a model for clinical application, a 7-gene panel was established (AUC = 0.927, 95% CI: 0.877-0.977) and successfully validated by multisampling. (AUC = 0.892, 95% CI: 0.878-0.906). GO and KEGG analyses suggest that FMO1 and FMO2 regulate the extracellular matrix and cell adhesion. FMO1 and FMO2 were positively correlated with the immune score of GC, and their expression was associated with the infiltration of immune cells.

Conclusion

PM in GC is strongly correlated with FMOs. Overall, FMO1 and FMO2 have huge prospects for application as novel diagnostic and therapeutic targets.

Response Evaluation in Patients with Peritoneal Metastasis Treated with Pressurized IntraPeritoneal Aerosol Chemotherapy (PIPAC)

Pressurized intraperitoneal aerosol chemotherapy (PIPAC) directed therapy emerged as a treatment of peritoneal metastasis (PM) a decade ago. The response assessment of PIPAC is not uniform. This narrative review describes non-invasive and invasive methods for response evaluation of PIPAC and summarizes their current status. PubMed and clinicaltrials.gov were searched for eligible publications, and data were reported on an intention-to-treat basis. The peritoneal regression grading score (PRGS) showed a response in 18-58% of patients after two PIPACs. Five studies showed a cytological response in ascites or peritoneal lavage fluid in 6-15% of the patients. The proportion of patients with malignant cytology decreased between the first and third PIPAC. A computed tomography showed stable or regressive disease following PIPAC in 15-78% of patients. The peritoneal cancer index was mainly used as a demographic variable, but prospective studies reported a response to treatment in 57-72% of patients. The role of serum biomarkers of cancer or inflammation in the selection of candidates for and responders to PIPAC is not fully evaluated. In conclusion, response evaluation after PIPAC in patients with PM remains difficult, but PRGS seems to be the most promising response evaluation modality.