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 (ADC(0) ). Fifteen to 20 hours after tumors received 15 Gy, mice were scanned again and ADC values (ADC(1) ) were measured.

RESULTS

ADC(0) and ADC(1) values of the CNE1 group showed no significant difference (P = .692). The difference between the ADC(0) and ADC(1) values of the CNE2 group was statistically significant (P < .001). ADC(0) values of the two groups exhibited no statistically significant difference (P = .204). ADC(1) , ADC(1-0) , and ΔADC of the two groups exhibited statistically significant differences (P < .001; P = .001 and .002, respectively). After irradiation, volume changes ΔV(8) , ΔV(10) , and ΔV(12) of two groups were statistically different (all P < .001). Pearson correlation analysis showed ADC(1-0) and ΔADC were positively correlated with ΔV(8) , ΔV(10) , and ΔV(12) . The cut point was found by means of a receiver operating characteristic curve, and the ΔV(12) 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.