Due to the existence of heterogeneity, the prognosis of lung cancer varies greatly, so it is very important to screen relevant prognostic indicators. With the advancement of image analysis tools, tumor metabolic characteristics can now be assessed rapidly and consistently with no interobserver variability, with the potential for routine assessment in clinical practice. Various molecular imaging techniques have been developed to predict the tumor response to therapy, such as FDG PET 9, 18F-fluorothymidine (FLT) PET 10, 18F-fluroerythronitroimidazole (FETNIM) PET 11 and 18F-fluoromisonidazole (FMISO) PET 12.
Studies on the capabilities of 18F-alfatide II PET/CT have increased in recent years and have shown the advantages of this imaging technique for evaluating chest tumors due to the high in vivo TBR identified in PET imaging 5,8,13. In this study, sex, histology, stage, SUVP, SUVLN, TBRP−LN, TBRLN and TBRP were significantly associated with PFS and OS in the correlation analysis, and SUVLN before treatment in 18F-alfatide II PET/CT and TNM staging were revealed to independently predict PFS and OS of lung cancer through multivariate Cox regression analysis.
Why is 18F-alfatide II PET/CT useful in predicting survival in patients with lung cancer? 18F-alfatide II can bind to integrin αvβ3, which is upregulated in the activated endothelial cells with tumor angiogenesis, with high affinity and specificity. Li et al. reported that 18F-alfatide II uptake on PET/CT can predict the response to antiangiogenic therapy, with higher 18F-alfatide II uptake in tumors predicting a better response to apatinib therapy in a variety of tumors 14. Luan X et al. found that SUVP and tumor-to-blood ratios can predict the short-term outcome of concurrent chemoradiotherapy (CCRT) in patients with advanced NSCLC. Patients with lower SUVP and tumor-to-blood ratios responded to CCRT (all P < 0.05) 6.
Lymph metastasis is a well-characterized negative factor affecting survival in cancer patients and reducing tumor staging. Wu C et al. suggested that tumors often drive inflammation both in primary tumor tissue and in tumor-draining lymph nodes, and the inflamed tissue can also show high uptake of 18F-FDG and 18F-alfatide II 4. Chen et al. found that RGD PET provides better imaging of mediastinal lymph nodes and contralateral metastases than 18F-FDG by providing better imaging 15,16. Studies have also indicated that SUVLN both in 18F-FDG PET/CT and in 18F-alfatide II PET/CT is influenced by the pathological stage, lymph node states, and tumor differentiation and that it may serve as a useful new parameter for risk stratification with esophageal squamous cell carcinoma 17. In this study, we found that SUVLN not only is significantly negative associated with PFS and OS but also may be an independent predictor for PFS and OS in patients with lung cancer. The SUVs from 18F-alfatide PET/CT imaging represent the expression of integrin αvβ3: the higher the expression is, the higher the malignant degree of the tumor and the worse the prognosis.
In this study, it was found that the PFS and OS of patients with lung cancer in stages I-II were better than those in stages III-IV. TNM staging is recognized as one of the useful factors for predicting tumor survival 13,18. Clinical studies have confirmed that 18F-alfatide II PET/CT offers good differentiation and imaging of lung cancer 5,13, breast cancer 19, esophageal cancer 17, glioblastoma 20, brain metastases 21, and other diseases. The sensitivity, specificity, and accuracy of 18F-alfatide PET/CT in the diagnosis of lymph node metastasis of NSCLC were 92.7%, 95.7% and 95.4%, respectively 16. 18F-alfatide II PET/CT is superior to 18F-FDG PET/CT in the detection of skeletal and bone marrow metastases, with nearly 100% sensitivity for osteolytic, mixed and bone marrow lesions 22. The above studies show that 18F-alfatide II PET/CT is capable of accurately measuring TNM of lung cancer.
This study has several limitations in addition to the relatively small subgroup sample sizes. First, it was a single-center study. In addition, 18F-alfatide II PET/CT imaging was performed only once in patients with lung cancer before treatment, but not during or after treatment. The idea that changes of SUVs in 18F-alfatide II PET/CT are related to prognosis is a proposition worth exploring. Nevertheless, these shortcomings diminish neither the potential of our findings nor the importance of dedicated prospective investigations to corroborate these findings.