Early changes in apparent diffusion coefficients predict radiosensitivity of human nasopharyngeal carcinoma xenografts

Objectives/Hypothesis: Our objective was to predict the radiosensitivity of human nasopharyngeal carcinoma xenografts in nude mice models through an examination of early changes in apparent diffusion coefficient (ADC) values. Study Design: Randomized. Methods: BALB/c-nu nude mice (n 20) were divided into two groups that were subcutaneously injected with CNE1 or CNE2 cell lines. Xenograft volumes were measured after tumor formation, mice were scanned with a diffusion-weighted imaging sequence, and the mean ADC values were measured (ADC0). Fifteen to 20 hours after tumors received 15 Gy, mice were scanned again and ADC values (ADC1) were measured. Results: ADC0 and ADC1 values of the CNE1 group showed no significant difference (P.692). The difference between the ADC0 and ADC1 values of the CNE2 group was statistically significant (P <.001). ADC0 values of the two groups exhibited no statistically significant difference (P.204). ADC1, ADC1-0, and DADC of the two groups exhibited statistically significant differences (P <.001; P.001 and.002, respectively). After irradiation, volume changes DV8, DV10, and DV12 of two groups were statistically different (all P <.001). Pearson correlation analysis showed ADC1-0 and DADC were positively correlated with DV8, DV10, and DV12. The cut point was found by means of a receiver operating characteristic curve, and the DV12 of the two redivided groups showed a statistically significant difference (P.001). Conclusions: This study found that changes in ADC values correlated with volume changes after irradiation. Therefore, ADC values have the potential to predict the radiosensitivity of nasopharyngeal carcinoma xenografts.