2633 - Different Detection Rates of Brain Metastasis in Different Pathological Types of Lung Cancer by ¹⁸F-FAPI PET/CT

Y. Wei¹, H. Li², and J. Yu²; ¹Department of Radiation Oncology and Shandong Provincial Key Laboratory of Radiation Oncology, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, Shandong, China, ²Department of Radiation Oncology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, China

Purpose/Objective(s): The purpose of this study was to evaluate the utility of fluorine-18-fibroblast activation protein inhibitor (¹⁸F-FAPI) PET/CT for detecting brain metastasis (BM) in different pathological types of lung cancer using craniocerebral MRI as the standard. Materials/

Methods: From December 2020 to October 2021, patients with pathologically confirmed lung cancer and suspected BM were prospectively enrolled and underwent paired ¹⁸F-FAPI PET/CT and MRI. The number of BMs and maximum tumor diameter were measured by MRI. The maximum and peak standardized uptake values (SUVmax and SUVpeak, respectively) and tumor-to-background ratio (TBR) on ¹⁸F-FAPI PET/CT in BMs were evaluated.
Results: A total of 76 BM lesions in 18 patients (male, n=11; female, n=7) were evaluated. Overall, 23 of 76 BM lesions were detected by ¹⁸F-FAPI PET/CT. The detection rate of BM in adenocarcinoma [48.28% (14/29)] was significantly higher than that in large cell carcinoma [16.67% (4/24), P=0.016] and small cell carcinoma [0% (0/9), P=0.009], but not significantly different from that in squamous carcinoma [35.71% (5/14), P=0.437]. The BM detection rate was higher in squamous carcinoma than in small cell carcinoma (P=0.043), but did not differ significantly between large cell carcinoma and small cell carcinoma or squamous carcinoma (P=0.183 and 0.191, respectively). The SUVmax, SUVpeak, and TBR of ¹⁸F-FAPI in BM showed no significant differences among adenocarcinoma, squamous carcinoma, and large cell carcinoma (all P>0.05). A moderate positive correlation with tumor diameter was observed for SUVmax (r=0.42, P=0.04), but not SUVpeak or TBR (r=0.39, P=0.07; r=0.29, P=0.18).
Conclusion: This study revealed differences in the detection rates of BM in lung cancer types by ¹⁸F-FAPI PET/CT, with the highest and lowest detection rates in adenocarcinoma and small cell carcinoma, respectively, which may be valuable for predicting the prognosis of lung cancer patients with BM.