EJNMMI RESEARCH · Published 2026-06-10 · DOI 10.1186/s13550-026-01452-6
Xue Cai, Qin Wang, Qingfan Hao, Jian Zhang
Abstract Background IgG4-related disease (IgG4-RD) lacks standardized imaging criteria. This study systematically reviewed head-to-head comparisons of 68Ga-FAPI and 18F-FDG PET/CT to clarify their complementary roles in diagnosing and staging IgG4-RD. Main body Three high-quality studies (n = 90) were pooled. 68Ga-FAPI showed significantly higher SUVmax and target-to-background ratios (TBR) in parenchymal organs (pancreas, salivary glands) vs. 18F-FDG (P < 0.001), offering superior lesion contrast. While 18F-FDG detected more lymph node activity, 68Ga-FAPI identified 136 vs. 78 total lesions, improving systemic burden assessment. Pathology correlated FAPI with fibrosis and FDG with inflammation, defining a “flip-flop” pattern. A FAPI/FDG ratio ≥ 1.5 predicted relapse risk. Conclusion 68Ga-FAPI excels in parenchymal organ involvement, while FDG highlights inflammatory lymphadenopathy. Combining both tracers enables multimodal evaluation of fibroinflammatory activity, guiding personalized management and prognostication in IgG4-RD.
Abstract from DOAJ. Public domain (CC0 1.0).
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Cai, X., Wang, Q., Hao, Q., et al. (2026). Complementary roles of 68Ga-FAPI and 18 F-FDG PET/CT in evaluating IgG4-related disease: a systematic review and pooled analysis. EJNMMI RESEARCH. https://doi.org/10.1186/s13550-026-01452-6