¹⁸F-FLT and ¹⁸F-FLT PET in monitoring the early response of esophageal carcinoma model after irradiation

Objective: To explore the value of 3'-deoxy-3'-¹⁸F-fluorothymidine (¹⁸F-FLT) and ¹⁸F-FLT PET in monitoring the early response of esophageal carcinoma model after irradiation. Methods: After 2, 4 and 8 h of irradiation with different doses (5, 10, 15 Gy) to the esophageal carcinoma cells in vitro, the uptake ratio of ¹⁸F-FLT and the relative survival rate and ATP levels were measured. Twenty-four BALB/c nu/nu mice bearing esophageal carcinoma were treated with single-dose X-ray irradiation of 10 Gy. Tumor uptake of ¹⁸F-FLT (tumor-to-non tumor, T/NT) was calculated before and after irradiation at l, 7 and 15 d. Expression of proliferating cell nuclear antigen (PCNA) and Ki-67 were determined in untreated and treated tumors. Results: In the control group, the uptake ratio of ¹⁸F-FLT is (4.00 ± 0.42)%. After irradiation with 5, 10, 15 Gy, the uptake ratio of ¹⁸F-FLT decreased to (3.65 ± 0.41)%, (3.17 ± 0.45)% and (2.53 ±0.28)% at 2 h, and it decreased to (2.84 ± 0.35)%, (2.58 ± 0.39)% and (1.80 ± 0.22)% at 4 h, and it decreased to (2.7l ± 0.23)%, (1.89 ± 0.31)% and (1.44 ± 0.20)% at 8 h, respectively. The difference of the relative survival rate of esophageal carcinoma cells after 2, 4 and 8 h of irradiation with different doses (5, 10, 15 Gy) is not statistically significant (P > O.05). Line regression analysis indicated a significant correlation between ¹⁸F-FLT and ATP levels (r = 0.887, P < O.01). Tumor uptake of ¹⁸F-FLT presents a higher uptake. The ¹⁸F-FLT tumor-to-non tumor uptake ratio in xenografts is 2.24 ± 0.06. The T/NT uptake ratio decreased to 1.99 ± 0.09, 1.85 ± 0.04 and l.15 ± 0.10 after irradiation at l, 7 and 15 d. Tumor uptake of ¹⁸FFLT was closely correlated with PCNA and Ki-67 expression (r = 0.83, P < 0.001 and r = 0. 88, P < 0.001). Conclusions: The uptake ratio changes of ¹⁸F-FLT in the esophageal carcinoma cells and in the tumor tissues may reflect the early biological response of esophageal carcinoma model after irradiation. The result suggests that ¹⁸F-FLT may be used to monitor the early response of esophageal carcinoma after irradiation. The clinical investigations need to be undertaken. (authors)