[18F]FAPI adds value to [18F]FDG PET/CT for diagnosing lymph node metastases in stage I-IIIA non-small cell lung cancer: a prospective study
Youcai Li, Yin Zhang, Zhihua Guo, Peng Hou, Jie Lv, Ke Miao, Shaoyu Liu, Siwen Li, Weiqiang Yin, Jianxing He, Xinlu Wang
Abstract
Abstract Background This study investigates the value of fluorine 18 ([ 18 F])-labeled fibroblast activation protein inhibitor (FAPI) for lymph node (LN) metastases in patients with stage I-IIIA non-small cell lung cancer (NSCLC). Methods From November 2021 to October 2022, 53 patients with stage I-IIIA NSCLC who underwent radical resection were prospectively included. [ 18 F]-fluorodeoxyglucose (FDG) and [ 18 F]FAPI examinations were performed within one week. LN staging was validated using surgical and pathological findings. [ 18 F]FDG and [ 18 F]FAPI uptake was compared using the Wilcoxon signed-ranks test. Furthermore, the diagnostic value of nodal groups was investigated. Results In 53 patients (median age, 64 years, range: 31–76 years), the specificity of [ 18 F]FAPI for detecting LN metastasis was significantly higher than that of [ 18 F]FDG ( P < 0.001). High LN risk category, greater LN short-axis dimension(≥ 1.0 cm), absence of LN calcification or high-attenuation, and higher LN FDG SUV max (≥ 10.1) were risk factors for LN metastasis( P < 0.05). The concurrence of these four risk factors accurately predicted LN metastases (Positive Predictive Value [PPV] 100%), whereas the presence of one to three risk factors was unable to accurately discriminate the nature of LNs (PPV 21.7%). Adding [ 18 F]FAPI in this circumstance improved the diagnostic value. LNs with an [ 18 F]FAPI SUV max <6.2 were diagnosed as benign (Negative Predictive Value 93.8%), and LNs with an [ 18 F]FAPI SUV max ≥6.2 without calcification or high-attenuation were diagnosed as LN metastasis (PPV 87.5%). Ultimately, the integration of [ 18 F]FDG and [ 18 F]FAPI PET/CT resulted in the highest accuracy for N stage (83.0%) and clinical decision revisions for 29 patients. Conclusion In patients with stage I-IIIA NSCLC, [ 18 F]FAPI contributed additional valuable information to reduce LN diagnostic uncertainties after [ 18 F]FDG PET/CT. Integrating [ 18 F]FDG and [ 18 F]FAPI PET/CT resulted in more precise clinical decisions. Trial registration The Chinese Clinical Trial Registry: ChiCTR2100044944 (Registered: 1 April 2021, https://www.chictr.org.cn/showprojEN.html?proj=123995 ).