Lymph Node Maximum Uptake of 18F-ALF-NOTA-PRGD2 II PET/CT Predicts Lung Cancer Survival

Tumor angiogenesis plays a key role in tumor growth, development, and metastasis, so the exploratory study of tumor neovascularization imaging is one of the potential methods to predict survival. This study aims to examine the predictive capacity of 18 F-ALF-NOTA-PRGD2 II (denoted 18 F-Alfatide II) positron emission tomography (PET)/computed tomography (CT) before antitumor therapy (ATR) in patients with lung cancer. Results The median follow-up was 31 (1.3~57.0) months. Among the patients, 6 were lost to follow-up. The overall survival (OS) and progression-free survival (PFS) were 40.0 (3.50~57.0) months and 21.30 (2.0~56.0) months, respectively. The maximum uptake values (SUV max ) of the metastatic lymph nodes (SUV LN ) and tumor node metastasis (TNM) staging were signicant predictors of PFS and OS (all P<0.05) in a multivariate Cox regression analysis. Statistical signicance was not reached by any other variable in the multivariate analysis. Receiver operating curve (ROC) analysis for survival revealed an area under the curve of 0.93 (P<0.001) for SUV LN and 0.96 for the TNM stage (P<0.001). The SUV LN and TNM stage cutoff values were 2.50 and II, and their sensitivity, specicity and positive and negative prediction were 77.42%, 80.0% and 82.76% and 74.07%; and 87.10%, 60.0% and 72.97% and 78.95%, respectively. Patients with a lower SUV LN and early stage had a longer PFS and OS (all P<0.05).


Background
Lung cancer remains the leading cause of cancer incidence and mortality worldwide 1 , with 2.1 million new lung cancer cases and 1.8 million deaths predicted in 2018, representing close to 1 in 5 (18.4%) cancer deaths 2 . The treatment methods are surgery, radiotherapy, chemotherapy, targeting and so on; the therapeutic effect is poor, and there is a signi cant difference in outcomes 3 , the main reason for which is the widespread heterogeneity of tumors. The functional molecular imaging of positron emission tomography (PET) can be used to detect the internal characteristics of the whole tumor, such as glucose metabolism, angiogenesis, and hypoxia. With the development of individualized functional metabolic imaging, molecular imaging techniques are promising to predict the prognosis of lung cancer.
Arginine-glycine-aspartic acid peptide (Arg-Gly-Asp, RGD) enables a new kind of positron drug, which is approved for clinical trials and can safely 4 and effectively image the angiogenesis of non-small-cell lung cancer (NSCLC) 5,6 with clarity and desirable image contrast. Tumor angiogenesis plays an important role in regulating growth, local invasiveness, and metastatic potential 7 . Previously, we performed a pilot clinical study that demonstrated the feasibility of using 18 F-ALF-NOTA-PRGD2 II (denoted 18 F-alfatide II) PET/computed tomography (CT) to predict the short-term outcome of concurrent chemoradiotherapy in patients with advanced NSCLC 6 . However, there are few reports on whether 18 F-alfatide II can predict the long-term survival of lung cancer.
In the present study, we analyze standard uptake values (SUVs) of 18 F-alfatide II on PET/CT before antitumor therapy (ATR) and explore its predictive value in overall survival (OS) and progression-free survival (PFS) of patients with lung cancer.

Patients
Between June 10, 2015, and Dec 28, 2016, a total of sixty-two patients with pathologically con rmed lung cancer were enrolled in the study. This prospective study was approved by the local ethics committee of Shandong Cancer Hospital and Institute, and each patient gave written informed consent before the study. All patients were treated in Shandong Cancer Hospital and satis ed the following criteria: diagnosed by histological and imaging examination such as CT or 18 F-uorodeoxyglucose (FDG) PET/CT; an Eastern Cooperative Oncology Group (ECOG) score of ≤ 1; clearly measurable metastatic lymph nodes and primary tumors; and no ATR before the 18 F-alfatide II PET/CT scan.

Radiotracer preparation
A simple lyophilization kit for labeling PRGD2 peptide was purchased from the Jiangsu Institute of Nuclear Medicine, and the synthesis process was carried out by reference to the previous study 8 . The radiochemical purity of the 18 F-alfatide exceeded 99%, and its speci c radioactivity exceeded 37 GBq (1,000 mCi)/µmol.

PET/CT scanning
Patients were given an intravenous injection of 4.81 MBq/kg (0.12 mCi/kg) 18 F-alfatide II and allowed to rest for approximately 60 minutes. Patients were not requested to fast but were requested to specify their recent diet to allow estimation of blood glucose levels. Scanning was performed with an integrated inline PET/CT system (GEMINI TF Big Bore; Philips Healthcare). PET images were acquired from the head to the thigh, and the spiral CT component was obtained with an X-ray tube voltage peak of 120 kV, 300 mAs. A full-ring dedicated PET scan of the same axial range followed. The patients exhibited normal shallow respiration during image acquisition. The images were attenuation-corrected with the transmission data from CT. The attenuation-corrected PET images, CT images, and fused PET/CT images, displayed as coronal, sagittal, and transaxial slices, were viewed on a MEDEX workstation (Beijing, China).

Image analysis
Two experienced nuclear medicine physicians assessed the 18 F-alfatide II PET/CT images visually, referring to the PET fusion and CT images, until consensus was reached. The acquired 18 F-alfatide II PET/CT data were transferred into a workstation in the DICOM format. The radiotracer concentration in the region of interest (ROI) was normalized to the injected dose per kilogram of the patients' body weight to derive the standardized uptake values (SUVs). PET/CT parameters such as the maximum uptake values for the primary tumor (SUV P ) or metastatic lymph node (SUV LN ) and the mean SUVs for the mediastinal blood pool (SUV blood ) were generated using a vendor-provided automated contouring program.
In addition, tumor-to-background ratios (TBRs) were calculated. Then, the SUV ratios of the primary tumor to blood pool, metastatic lymph node to blood pool, and primary tumor to metastatic lymph node were calculated and are denoted TBR P , TBR LN , and TBR P−LN , respectively.

Antitumor therapy
Surgery is the rst choice for patients who can be surgically resected. Patients without surgical indications or who are unable to tolerate surgery should choose comprehensive treatment based on radiotherapy and chemotherapy. The chemotherapy scheme is a platinum-based dual-drug.
An intensity-modulated radiotherapy technique (IMRT) or a three-dimensional conformal radiotherapy technique (3D-CRT) was delivered to patients with megavoltage equipment (6 MV). Radiotherapy was given as the conventionally fractionated regimen, 180 cGy to 200 cGy for ve days per week, and the total dose administered to patients ranged from 5040 cGy to 6600 cGy (median dose, 6000 cGy).
The pathological type of adenocarcinoma is routine gene detection, and patients with targeted treatment can choose epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) drug therapy.

End points and assessments
The two primary end points were PFS (as assessed by investigators according to RECIST criteria) and OS in all patients with lung cancer. Patients were followed up by enhanced CT every 6 weeks during treatment, every 2 months in the rst year after treatment, and every six months from the second year after treatment.
The OS time was from the date of diagnosis to the date of follow-up or death, and the date of PFS was from the date of diagnosis to the date of tumor recurrence or progression.
General case data that might have affected the prognosis of the patients were recorded, including the sex, age, pathological type, and TNM stage (clinical stage or postoperative stage).

Statistical analysis
Statistical analysis was performed using IBM SPSS Statistics for Windows version 20.0 (IBM, Armonk, USA).
The Pearson test was used for continuous variables in correlation analysis, and the Spearman test was used for classi ed variables. Data derived from SUV measurements were analyzed for correlation with survival using receiver operating characteristic (ROC) curve analysis and the Youden index for independencies using the χ 2 test. The PFS and OS were assessed by Kaplan-Meier analysis. Cox regression proportional hazards models were used to obtain hazard ratio estimates of signi cant parameters derived from univariate analysis using P ≤ 0.1 for the parameters to qualify for multivariate analysis. All tests were 2-sided, and P < 0.05 was considered statistically signi cant.

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Of the sixty-two patients (Table 1) Table 3 shows the correlation between different factors with PFS and OS. SUV LN and stage were negatively correlated with OS and PFS, all P < 0.05.  The ROC curve analysis of the respective parameters, applying survival as the dichotomous characteristic, revealed a signi cant area under the curve of 0.93 (P < 0.001) for SUV LN (Fig. 1). At a cutoff value of 2.50, derived by the Youden index, the sensitivity, speci city, and positive and negative prediction were 77.42%, 80.0%, and 82.76% and 74.07%, respectively. A signi cant area under the curve of 0.96 (P < 0.001) was found for stage ( Fig. 1). At a cutoff value of II, derived by the Youden index, the sensitivity, speci city, and positive and negative prediction were 87.10%, 60.0%, and 72.97% and 78.95%, respectively.
The corresponding Kaplan-Meier curves are given in Fig. 2

Discussion
Due to the existence of heterogeneity, the prognosis of lung cancer varies greatly, so it is very important to with esophageal squamous cell carcinoma 17 . In this study, we found that SUV LN not only is signi cantly 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 18 F-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 con rmed that 18

Conclusion
In this prospectively study, it was con rmed that the high uptake of SUV LN in 18

Declarations
Ethics approval and consent to participate This prospective study was approved by the local ethics committee of Shandong Cancer Hospital and Institute, and each patient gave written informed consent before the study.

Consent for publication
All the personal data involved in this article have been signed with informed consent.

Availability of data and material
The datasets used and/or analyzed during the current study are available form the corresponding author on reasonable request.