Abstract
Background Accurate clinical staging is crucial to managing gastrointestinal cancer, but fluorine 18 (18F) fluorodeoxyglucose (FDG) PET/CT has limitations. Targeting fibroblast-activation protein is a newer diagnostic approach for the visualization of tumor stroma, and gallium 68 (68Ga)-labeled fibroblast-activation protein inhibitors (FAPIs), hereafter 68Ga-FAPIs, present a promising alternative to 18F-FDG. Purpose To compare the diagnostic efficacy of 68Ga-FAPI PET/CT in primary and metastatic lesions of gastrointestinal malignancies with that of 18F-FDG PET/CT. Materials and Methods Images from patients with gastric, duodenal, and colorectal cancers who underwent contemporaneous 18F-FDG and 68Ga-FAPI PET/CT between October 2019 through June 2020 were retrospectively analyzed. 18F-FDG and 68Ga-FAPI uptakes were compared by using the Wilcoxon signed-rank test. The McNemar test was used to compare the diagnostic performance between the two techniques. Results Thirty-five patients (median age, 64 years [interquartile range, 53-68 years]; 18 men) were evaluated. In treatment-naive patients (n = 19), 68Ga-FAPI PET/CT led to upstaging of the clinical TNM stage in four (21%) patients compared with 18F-FDG PET/CT. Tracer uptake was higher with 68Ga-FAPI PET/CT than with 18F-FDG PET/CT in primary lesions (gastric cancer: 12.7 vs 3.7, respectively, P = .003; colorectal cancer: 15.9 vs 7.9, P = .03), involved lymph nodes (6.7 vs 2.4, P < .001), and bone and visceral metastases (liver metastases: 9.7 vs 5.2, P < .001; peritoneal metastases: 8.4 vs 3.6, P < .001; bone metastases: 4.3 vs 2.2, P < .001; lung metastases: 4.4 vs 1.9, P = .01). In addition, the sensitivity of 68Ga-FAPI PET/CT was higher than that of 18F-FDG PET/CT in the detection of primary tumors (100% [19 of 19] vs 53% [10 of 19], respectively; P = .004), lymph nodes (79% [22 of 28] vs 54% [15 of 28], P < .001), and bone and visceral metastases (89% [31 of 35] vs 57% [20 of 35], P < .001). Conclusion Gallium 68 fibroblast-activation protein inhibitor PET/CT was superior to fluorine 18 fluorodeoxyglucose PET/CT in the detection of primary and metastatic lesions in gastric, duodenal, and colorectal cancers, with higher tracer uptake in most primary and metastatic lesions. Published under a CC BY 4.0 license.
Highlights
Key Results n Compared with fluorine 18 (18F) fluorodeoxyglucose (FDG) PET/ CT, gallium 68 (68Ga)–labeled fibroblast-activation protein inhibitor (FAPI) PET/CT revealed more metastatic lesions and led to upstaging of TNM stage in 21% of patients, especially in peritoneal carcinomatosis, liver metastases, and bone metastases
Patients were consecutively recruited for enrollment in this study from October 2019 through June 2020 at the First Affiliated Hospital of Xiamen University. 68Ga-FAPI PET/CT was performed after 18F-FDG PET/CT for comparative purposes, without affecting the patients' care
Our study demonstrated that 68Ga-FAPI PET/CT was more sensitive for identifying primary tumors (100% [19 of 19] vs 53% [10 of 19], respectively; P = .004) in gastric, duodenal, and colorectal cancers than was 18F-FDG PET/CT because of its favorable tumor-to-background contrast (7.6 vs 2.2, P, .001) and low uptake in the gastrointestinal tract
Summary
Images from patients with gastric, duodenal, and colorectal cancers who underwent contemporaneous 18F-FDG and 68Ga-FAPI PET/CT between October 2019 through June 2020 were retrospectively analyzed. 18F-FDG and 68GaFAPI uptakes were compared by using the Wilcoxon signed-rank test. Images from patients with gastric, duodenal, and colorectal cancers who underwent contemporaneous 18F-FDG and 68Ga-FAPI PET/CT between October 2019 through June 2020 were retrospectively analyzed. The McNemar test was used to compare the diagnostic performance between the two techniques Patients This single-center retrospective study was performed at the First Affiliated Hospital of Xiamen University, and the study protocol was approved by the institutional review board (ClinicalTrials.gov identifier: NCT04416165). Exclusion criteria were (a) patients with nonmalignant disease, (b) pregnant patients, (c) patients whose treatment had already started before their 68Ga-FAPI PET/CT examination, and (d) the inability or unwillingness of the research participant, parent, or legal representative to provide written informed consent. Histopathologic examination of biopsy or resected surgical specimens served as the reference standard for the final diagnosis
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