The experimental study of 18F-FLT in monitoring the early biologic response of esophageal carcinoma to irradiation

Objective To explore the value of 18F-FLT in monitoring the early response of esophageal carcinoma cells and tumor model to irradiation.Methods After 2,4 and 8 h of irradiation with different doses (5,10,15 Gy) in vitro,the uptake ratio of 18F-FLT and the relative survival rate and ATP levels in esophageal carcinoma (Eca)-109 cells were measured.Twenty-four BALB/c nu/nu mice bearing esophageal carcinoma were divided into 4 groups by random number table method.Three groups were treated with 10 Gy X-ray irradiation and the other group was control group (0 Gy).Tumor uptake of 18F-FLT(T/NT) was calculated before (control group)and on the 1st,7th,15th d after irradiation(3 treated groups).The mice were sacrificed after imaging and the expressions of proliferating cell nuclear antigen (PCNA) and Ki67 were detected.One-way analysis of variance,two-sample t test and Pearson correlation were applied for statistical analysis.Results The uptake ratio of 18F-FLT in Eca-109 cells before irradiation was (4.00± 0.42)％.After irradiation with 5,10,15 Gy,the uptake ratios decreased to (3.65±0.41)％,(3.17± 0.45)％ and (2.53±0.28)％ at 2 h,(2.84±0.35)％,(2.58±0.39)％ and (1.80±0.22)％ at 4 h,(2.71± 0.23) ％,(1.89±0.31) ％ and (1.44±0.20) ％ at 8 h,respectively.The relative survival rates of Eca-109 cells after 2,4 and 8 h of irradiation with different doses (5,10,15 Gy) were not significantly different (F=4.02,P＞0.05).There was a significant correlation between 18F-FLT and ATP levels(r =0.89,P＜0.01).18F-FLT PET imaging showed the tumor had a high uptake.The ratio in xenografts was 2.24±0.06 before irradiation.It decreased to 1.99±0.09,1.85±0.04 and 1.15±0.10 on the 1st,7th,15th d after irradiation.Tumor uptake of 18F-FLT was closely correlated with PCNA and Ki67 expression (r=0.83,0.88,both P＜0.01).Conclusions The uptake changes of 18F-FLT in the esophageal carcinoma cells and tumor tissues may reflect the early biological response of esophageal carcinoma to irradiation.18F-FLT PET may be used to monitor the early response of esophageal carcinoma to irradiation. Key words: Esophageal neoplasms;  Tumor cell, cultured;  Radiotherapy;  Tomography, emission computed ;  Thymidine;  Mice, nude