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.