Utility of [68Ga]FAPI-04 and [18F]FDG dual-tracer PET/CT in the initial evaluation of gastric cancer

Abstract

Objectives We aimed to investigate the role of [68Ga]FAPI-04 and [18F]FDG dual-tracer PET/CT for the initial assessment of gastric cancer and to explore the factors associated with their uptake. Methods This study enrolled 62 patients with histopathologically confirmed gastric cancer. We compared the diagnostic performance of [68Ga]FAPI-04, [18F]FDG, and combined dual-tracer PET/CT. The standardized uptake value (SUV) and tumor-to-background ratio (TBR) were also measured, and the factors that influence tracer uptake were analyzed. Results [68Ga]FAPI-04 PET/CT detected more primary lesions (90.3% vs 77.4%, p = 0.008) and peritoneal metastases (91.7% vs 41.7%, p = 0.031) and demonstrated higher SUVmax and TBR values (p < 0.001) of primary lesions compared to [18F]FDG PET/CT. Dual-tracer PET/CT significantly improved the diagnostic sensitivity for the detection of distant metastases, compared with stand-alone [18F]FDG (97.1% vs 73.5%, p = 0.008) or [68Ga]FAPI-04 (97.1% vs 76.5%, p = 0.016) PET/CT. Subsequently, treatment strategies were changed in nine patients following [68Ga]FAPI-04 and [18F]FDG dual-tracer PET/CT. Nevertheless, [68Ga]FAPI-04 uptake was primarily influenced by the size and invasion depth of the tumor. Both [68Ga]FAPI-04 and [18F]FDG PET/CT showed limited sensitivity for detecting early gastric cancer (EGC) (37.5% vs 25.0%, p > 0.05). Conclusions In this initial study, [68Ga]FAPI-04 and [18F]FDG dual-tracer PET/CT were complementary and improved sensitivity for the detection of distant metastases pre-treatment in gastric cancer and could improve treatment stratification in the future. [68Ga]FAPI-04 had limited efficacy in detecting EGC. Key Points •[68Ga]FAPI-04 and[18F]FDG dual-tracer PET/CT are complementary to each other for improving diagnostic sensitivity in the initial evaluation of distant metastases from gastric cancer. •[68Ga]FAPI-04 PET/CT showed limited sensitivity in detecting EGC. • Need for further validation in a larger multi-centre prospective study.

Diagnostic Performance of Positron Emission Tomography with Fibroblast-Activating Protein Inhibitors in Gastric Cancer: A Systematic Review and Meta-Analysis

“…The mean/median values of the SUV max ranged from 5.5 to 18.81 for primary tumor and local recurrence, whereas they ranged from 4.3 to 9.2 and from 4.2 to 8.0 for lymph nodes and distant metastases, respectively. Compared to [ 18 F]FDG as a PET radiopharmaceutical, radiolabeled FAPis showed a greater number of positive patients and lesions; furthermore, when the [ 18 F]FDG and [ 68 Ga]Ga-FAPi-04 uptake were compared in positive lesions, FAP-targeted PET/CT showed overall higher values of the SUV max and TBR, even though the difference in the up-take of these two tracers was not statistically significant in some of the included studies [14,15,[17][18][19][20][21][22].…”

“…Moreover, seven studies were conducted in a single center [15][16][17][18][19][20][21], whereas the reamaining two were bicentric [14] and multicentric [22]. Seven out of nine studies disclosed financing resources in the text [14,16,[18][19][20][21][22]. Legend: CT: computed tomography, DOTA: 1,4,7,10-tetracetic-1,4,7,10-tetraazaciclododecan acid; FAPi: fibroblastactivation protein inhibitor, MR: magnetic resonance; NR: not reported; PET: positron emission tomography; TBR: target-to-background ratio.…”

“…Eight studies including 225 GC patients were selected for the pooled analysis of the DR of primary tumors on FAPi-targeted PET images. Overall, the DR of PET/CT or PET/MRI with FAPi-targeted PET for detecting primary GC ranged from 90.3% to 100% [14,15,[17][18][19][20][21][22] (Table 5). Legend: CI: confidence interval.…”

“…Eight studies evaluating the presence of distant metastases in 82 GC patients were selected for the pooled analysis of the DR of distant metastases on FAPi-targeted PET images. Overall, the DR of PET/CT or PET/MRI with FAPi-targeted PET for detecting GC distant metastases ranged from 91.67% to 100% [14,15,[17][18][19][20][21][22] (Table 6). The pooled DR of GC distant metastases was 96.90 (95% confidence interval: 90.90-99.41) (Figure 8).…”

Fibroblast Activation Protein Inhibitor (FAPI)-Based Theranostics—Where We Are at and Where We Are Heading: A Systematic Review

“…Nevertheless, this does not exclude FDG usage in gastric cancer, as coupling of these two tracers greatly increases sensitivity and specificity for distant lesions when compared to each single tracer alone. FAPI was still superior to FDG for primary lesions [ 39 ]. FAPI was also found to be better than FDG in detecting lymph node metastasis and peritoneal carcinomatosis, with higher mean and median SUV compared to FDG and with higher tumor to background and tumor to liver ratios.…”