From the Department of Nuclear Medicine (Y.L., Q.P., F.L.), Department of Rheumatology and Clinical Immunology, National Clinical Research Center for Dermatologic and Immunologic Diseases, the Ministry of Education Key Laboratory (Z.Z., M.L., H.Y.), and State Key Laboratory of Difficult, Severe and Rare Diseases (Z.Z., Y.W., X.J., H.Y.), Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, No. 1 Shuaifuyuan Wangfujing, Dongcheng District, Beijing 100730, PR China; Beijing Key Laboratory of Molecular Targeted Diagnosis and Therapy in Nuclear Medicine, Beijing, PR China (Y.L., Q.P., F.L.); Department of Endocrinology and Rheumatology, Taihe Hospital, Hubei University of Medicine, Shiyan, PR China (M.L.); and Medical Research Center, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, PR China (Y.W., X.J.).
Radiology. 2023 May;307(3):e222052. doi: 10.1148/radiol.222052. Epub 2023 Feb 28.
Background In rheumatoid arthritis (RA), fibroblast-like synoviocyte cells, which are involved in inflammation of the articular cartilage and bone, overexpress fibroblast activation protein (FAP). This is a feature that could be leveraged to improve imaging assessment of disease. Purpose To determine the performance of gallium 68 (Ga)-labeled FAP inhibitor (FAPI) in assessing joint disease activity of RA and to compare with fluorine 18 (F) fluorodeoxyglucose (FDG) imaging. Materials and Methods Twenty participants with RA (15 women; mean age, 55 years ± 10 [SD]) were prospectively enrolled from September 2020 to December 2021 and underwent clinical and laboratory assessment of disease activity and dual-tracer PET/CT (Ga-FAPI and F-FDG) imaging. Imaging-derived variables of PET joint count (the number of joints positive for RA at PET) and PET articular index (a sum of the points of the joints using a three-point scale) were correlated to clinical and laboratory variables of disease activity. Results The combined output of both PET/CT techniques helped detect 244 affected joints, all of which showed positive results at Ga-FAPI PET/CT. However, fifteen of 244 (6.1%) FAPI-avid joints in six of 20 (30%) participants were not detected at F-FDG PET/CT. The maximum standardized uptake value of the most affected joint in each participant was higher in Ga-FAPI than in F-FDG PET/CT (9.54 ± 4.92 vs 5.85 ± 2.81, respectively; = .001). The maximum standardized uptake values of the joints at both Ga-FAPI and F-FDG PET/CT were positively correlated with laboratory evaluation of C-reactive protein levels ( = 0.49 [ = .03] and 0.54 [ = .01], respectively). The PET joint count and PET articular index scores at Ga-FAPI PET/CT were also positively correlated with most clinical disease activity variables and radiographic progression of joint damage ( < .05). Conclusion In participants with rheumatoid arthritis who underwent gallium 68 fibroblast activation protein inhibitor PET/CT, the extent of joint involvement correlated with clinical and laboratory variables of disease activity and showed a greater amount and degree of affected joints than at fluorine 18 fluorodeoxyglucose PET/CT. Clinical trial registration no. NCT04514614 © RSNA, 2023 See also the editorial by Williams and Ahlman in this issue.
背景 在类风湿关节炎 (RA) 中，成纤维细胞样滑膜细胞参与关节软骨和骨的炎症，过度表达成纤维细胞激活蛋白 (FAP)。这一特征可用于改善疾病的影像学评估。目的 确定镓 68（Ga）标记的 FAP 抑制剂 (FAPI) 在评估 RA 关节疾病活动度方面的性能，并与氟 18（F）氟脱氧葡萄糖 (FDG) 成像进行比较。材料与方法 2020 年 9 月至 2021 年 12 月期间，前瞻性纳入 20 名 RA 患者（15 名女性；平均年龄，55 岁±10 [标准差]），并进行 RA 疾病活动度的临床和实验室评估以及双示踪剂 PET/CT（Ga-FAPI 和 F-FDG）成像。将成像衍生的 PET 关节计数（PET 检测到的 RA 关节数）和 PET 关节指数（使用三点量表的关节点数之和）与疾病活动度的临床和实验室变量相关联。结果 两种 PET/CT 技术的联合结果有助于检测到 244 个受累关节，这些关节在 Ga-FAPI PET/CT 上均呈阳性结果。然而，在 20 名参与者中的 6 名（30%）中，有 15 个（6.1%）FAPI 阳性关节在 F-FDG PET/CT 上未被检测到。每个参与者中受影响最严重关节的最大标准化摄取值在 Ga-FAPI 中高于 F-FDG PET/CT（分别为 9.54±4.92 和 5.85±2.81； =.001）。Ga-FAPI 和 F-FDG PET/CT 中关节的最大标准化摄取值与实验室评估的 C 反应蛋白水平呈正相关（ = 0.49 [ =.03] 和 0.54 [ =.01]）。Ga-FAPI PET/CT 的 PET 关节计数和 PET 关节指数评分也与大多数临床疾病活动变量和关节损伤的放射学进展呈正相关（ <.05）。结论 在接受镓 68 FAP 抑制剂 PET/CT 的类风湿关节炎患者中，关节受累程度与疾病活动度的临床和实验室变量相关，并且显示出比 F-FDG PET/CT 更多和更严重的受累关节。临床试验注册号 NCT04514614 ©RSNA，2023 也可参见本期 Williams 和 Ahlman 的社论。
