The preliminary study of 18F-FLT micro-PET/CT in predicting irradiation response of human nasopharyngeal carcinoma xenografts

Objectives We aim to investigate the value of 18F-FLT micro-PET/CT in predicting radiosensitivity of human nasopharyngeal carcinoma (NPC) xenografts in nude mice models.

Methods Twelve BALB/c-nu nude mice were randomly divided into two groups. They were subcutaneously injected with either CNE1 or CNE2 cell suspension. Xenograft volumes were measured after tumor formation. When the tumors reached nearly 10mm in diameter, the mice received 15Gy irradiation. Before and 24h after irradiation, 18F-FLT micro-PET/CT was performed. The region of interest (ROI) was manually drawn and the percentage of injected dose per gram of the tumor and muscle in the ROIs was recorded. Tumor-to-muscle ratio (T/M) was calculated and compared with volume changes.

Results After irradiation, CNE2 tumors decreased significantly while CNE1 tumors still grown and became stable after one week. Therefore, we could regard CNE2 group as an irradiation responder while CNE1 group as a non-responder. The value of T/M before irradiation (T/M0) in CNE1 mice was statistically lower than in CNE2 mice (1.73±0.51 versus 5.57±1.57; t=5.233, P=0.004). Besides, T/M decreased significantly in CNE2 group after irradiation (5.57±1.57 versus 3.59±1.32; t=10.67, P=0.001). By means of a receiver operating characteristic curve, the optimal cut value of T/M0 to predict radiosensitivity was 2.33 (sensitivity=100.0%, specificity=83.3%); as for T/M changes, it was -0.15 (Both sensitivity and specificity=100.0%).

Conclusions 18F-FLT micro-PET/CT have the potential to predict radiosensitivity in NPC xenografts nude mice models.

Research Support The study was supported by Youth Foundation of Shanghai Municipal Health Bureau (No. 20124Y092).