Abstract
Purpose
Radionuclide-labeled fibroblast-activation-protein inhibitor 04 (FAPI-04) as a positron emission tomography (PET) imaging tracer can reveal the localized expression of fibroblast activation protein (FAP), a cell-surface serine protease that is highly upregulated in more than 90% of epithelial carcinomas. In this study, we quantified the 18F-NOTA-FAPI-04 uptake on PET/computed tomography (CT) imaging in different pathological types of lung cancer and metastatic tumors.
Methods
We prospectively enrolled 61 patients with histopathologically proven primary lung cancer with metastases.PET/CT scanning was performed before any antitumor therapy and 1hour after injection of 235.10 ± 3.89 MBq of 18F-NOTA-FAPI-04. Maximum standard uptake values (SUVmax) were calculated for comparison among primary and metastatic lesions.
Results
Sixty-one patients with adenocarcinoma (ADC, n = 30), squamous cell carcinoma (SCC, n = 17), and small cell lung cancer (SCLC, n = 14) were enrolled in this study, and 61 primary tumors and 199 metastases were evaluated. No difference in18F-NOTA-FAPI-04 uptake was observed among primary ADC, SCC, and SCLC tumors (P = 0.198).Additionally, no difference in uptake was found between primary and metastatic lesions of lung cancer with the same pathological type (P > 0.05).However, uptake did differ among metastases of differing pathological type (P < 0.001). The SUVmax of metastatic lymph nodes was highest for SCC, followed by ADC and then SCLC (P < 0.001).The SUVmax of bone metastases also was highest for SCC, followed by ADC and SCLC (P < 0.05), but no difference was observed between ADC and SCLC. The SUVmax of metastases in other organs was higher in SCC cases than in ADC cases, but did not differ between SCC and SCLC or ADC and SCLC. Bone metastases exhibited higher uptake than those of lymph nodes and other organs in SCC and ADC (P < 0.05), but not in SCLC.
Conclusion
18F-NOTA-FAPI-04 PET/CT imaging revealed differences in FAP expression in metastases of lung cancer, with the highest expression specifically in bone metastases, and thus, may be valuable for distinguishing different pathological types of lung cancer.
Perspective on Fibroblast Activation Protein Specific PET/CT Imaging in Fibrotic Interstitial Lung Diseases: Imaging Fibrosis - a New Paradigm for Molecular Imaging?
