Predictive value of diffusion-weighted magnetic resonance imaging for cervical lymph node metastasis in nasopharyngeal carcinoma after chemoradiotherapy

Objective: Our aim is to investigate the predictive value of diffusion-weighted magnetic resonance imaging (DW-MRI) and apparent diffusion coefficient (ADC) values in cervical lymph node metastasis from nasopharyngeal carcinoma (NPC) after chemoradiatherapy. Methods: Between March 2010 and January 2013, 71 patients diagnosed with NPC were selected in our study. All patients received conventional magnetic resonance imaging (MRI) and diffusion-weighted imaging (DWI) examinations. The maximum cross-sectional area of metastatic lymph nodes was measured under sequence map of MRI, while the ADC value was measured under the selected region of interests (ROI) of ADC. Results: The maximum cross-sectional area of metastatic lymph nodes in both CR and non-CR group were retreated after chemotherapy compared with those before chemotherapy (all P<0.05), and they all presented an obvious retreat after radiotherapy (all P<0.001). The ADC value of metastatic lymph nodes after chemotherapy was evidently increased than those before chemotherapy (t = 13.27, P<0.001), and it increased more significantly after radiotherapy (t = 34.62, P<0.001). An obviously increasing trend was found in the mean ADC values of residual lymph nodes one month after treatment compared with those before treatment and no metastatic lymph nodes after treatment, which indicated a statistical significance (all P<0.001). The sensitivity, specificity, positive predictive value, negative predictive value, accuracy and area under curve (AUC) after treatment of NPC were 0.905, 0.680, 0.763, 0.583, 0.732 and 0.816, respectively, predicting by the threshold value setting by mean ADC value before treatment (8.11x10(-4) mm(2)/s). Conclusions: Our results demonstrated both DW-MRI and ADC value were of great predictive value inefficacy of chemoradiotherapy in NPC patients.