To assess the value of diffusion weighted imaging in early response to target therapy of non-small-cell lung cancer.

32 patients with non-small-cell lung cancer were selected in this study. MRI imaging,DWI and contrast-enhanced CT were performed before and after the first cycle of target therapy. These patients were divided into responding and non-responding group according to the tumor maximum diameter shrinkage rate after the second cycle of target therapy. ADC value of the tumor and the tumor maximum diameter between two groups were compared. MRI combined with DWI and contrast-enhanced CT were also compared for the imaging effect of tumor and obstructive atelectasis.

There were no significantly statistical difference in tumor maximum diameter between pre-therapy and post-therapy in both groups(P>0.05). After the first cycle of target therapy,the mean ADC values increased significantly in responding group (×10^-3 mm²/s:1.48±0.23 vs. 1.23±0.21, t= -15.45, P<0.01) while it showed little change in non-responding group (×10^-3 mm²/s:1.20±0.27 vs. 1.15±0.32, t= -1.69, P>0.05). The increase rate of ADC value in responding group was considerably higher than that in non-responding group(%:17.7±5.7 vs. 4.6±2.1, t=6.72, P<0.01). There was also significantly statistical difference in imaging effect of tumor and obstructive atelectasis between MRI combined with DWI(13 cases 81.3%) and contrast-enhanced CT(6 cases, 37.5%)(P<0.05).

Compared to contrast-enhanced CT, MRI combined with DWI present the boundary of lung tumor and atelectasis more clearly and provide a better tool for the measurement of tumor size and the assessment of therapy effect. ADC value can be a promising biomarker for detecting target therapy responses at an early stage in non-small-cell lung cancer.