Prospective Clinical Study Of Sequential ¹⁸F-FLT And ¹⁸F-FDG PET/CT Imaging In The Treatment Of Esophageal Cancer With Non Operative Radiotherapy

Background: The evaluation of curative effect and prognosis of non operative treatment of esophageal cancer mainly depends on imaging examination.However,traditional imaging techniques,such as CT or endoscopic ultrasonography,can only reflect the changes of anatomical structure before and after the treatment,so there are some limitations in the evaluation of therapeutic.¹⁸F-FDG PET/CT can accurately reflect the changes in the metabolic activity of tumor cells before and after treatment,so it is widely used in the treatment of patients with non operative esophageal cancer during radiotherapy and after radiotherapy.However,attention should be paid to the fact that radiation esophagitis is a very common complication after radiotherapy.Therefore,there are some limitations in the treatment of tumor recurrence by ¹⁸F-FDG PET/CT 。 So,it is urgent to explore a new type of positron imaging probe and molecular imaging technique in the evaluation of curative effect and prognosis of patients with esophageal cancer.Objective: ¹⁸F-FLT and ¹⁸F-FDG contrast imaging were used to study the relationship between the curative effect and imaging results of patients with squamous cell carcinoma of the esophagus,and to understand whether early ¹⁸F-FLT pet/ct and¹⁸F-FDG pet/ct scans were of value in predicting the efficacy.Methods: For 34 patients with esophageal squamous cell cancer,¹⁸F-FLT PET/CT and ¹⁸F-FDG PET/CT scan were performed,at baseline（pre treatment）and the end of the fourth week after radiotherapy or chemo radiotherapy（interim）,and the end of therapy completion for second weeks（final）.Standardized uptake values of SUV_max1),SUV_*max2),and SUV_max3) were measured on the pre,interim and final scans,respectively.At the same time,GTV FLT-PET and GTV FDG-PET were measured on the pre and interim scans.ΔSUV/ΔGTV said the difference between the two time points SUV_max/GTV.Analysis of correlation between imaging findings and follow-upResults:Regarding:On the basis of receiver operating characteristic analysis,the ¹⁸F-FLT PET/CT scans performed in the middle of the treatment were compared with those before and after the treatment,and the related imaging results predicted that the 2 year PFS and LRC showed the highest area under the curve（ΔSUV12,AUC of 0.812 for PFS,0.775 for LRC,with a cutoff of 60%;P=0.008）.In the interim PET-negative group（ΔSUV12>60% group）were more relevant between 2-year PFS and LRC in mid treatment than interim PET-positive group（PFS: 70.6% vs.35.2%,P=0.025;LRC:84.2% vs 52.9,P=0.046）.In ¹⁸F-FDG PET/CT,ΔSUV13 on the final¹⁸F-FDG PET/CT scan demonstrated better prediction（AUC of 0.812 for PFS,0.807 for LRC,with a cutoff of 75%;P=0.016）than those on pre/interim scans.On the final¹⁸F-FLT PET/CT scan(SUV_max) decrease≥75%)was associated with better clinical outcome（PFS: 73.3% vs.36.8%,P=0.022;LRC: 86.7%vs 52.6%,P=0.029）.These correlations were most significant in the subgroup of chemo radiotherapy.Conclusion: ¹⁸F-FLT scans in the middle of the treatment were better able to predict 2 years of PFS and LRC,which is correlated better with early responses and late outcomes than interim ¹⁸F-FDG PET/CT in esophageal squamous cancer patients.