18F-FAPI PET/CT for Assessing Inflammation-related Activity in Recurrent In-Stent Restenosis After Percutaneous Coronary Intervention: A Prospective Comparison With 18F-FDG.

BACKGROUND: Persistent inflammatory activity may contribute to recurrent in-stent restenosis (ISR) after percutaneous coronary intervention (PCI). This study aimed to evaluate the efficacy of 18F-FAPI PET/CT for detecting inflammation-related activity in recurrent ISR and to compare it with 18F-FDG PET/CT. PATIENTS AND METHODS: Patients with recurrent ISR after PCI and suspected persistent inflammatory mechanisms were prospectively enrolled. All patients underwent 18F-FAPI PET/CT, and 32 also underwent 18F-FDG PET/CT within 1 week. Patients were classified as having inflammation-related ISR or non-inflammation-related ISR by multidisciplinary adjudication. Visual and semiquantitative PET parameters were compared between groups and tracers. RESULTS: Forty-four patients (mean age, 56.8±10.3 y) were included, including 31 with inflammation-related ISR and 13 with non-inflammation-related ISR. 18F-FAPI PET/CT showed positive findings in all 31 patients with inflammation-related ISR, compared with 3 of 13 patients with non-inflammation-related ISR (100% vs. 23.1%). Visual score, SUVmax, SUVmean, TBRblood, and TBRliver were all significantly higher in inflammation-related ISR than in non-inflammation-related ISR (all P<0.001). In the dual-tracer subgroup (n=32), 18F-FAPI PET/CT detected all inflammation-related ISR cases (20/20, 100%), whereas 18F-FDG PET/CT detected 8 of 20 (40.0%) (P<0.001). Compared with 18F-FDG, 18F-FAPI showed higher visual scores and significantly greater tracer uptake in inflammation-related ISR (all P<0.05). CONCLUSIONS: 18F-FAPI PET/CT demonstrated higher detectability of inflammation-related activity in recurrent ISR and provided better lesion-to-background contrast than 18F-FDG PET/CT. These findings support its potential role in the noninvasive assessment of coronary inflammatory activity after PCI.