Diffusion-weighted imaging of nasopharyngeal carcinoma to predict distant metastases

Our study aimed to identify diffusion-weighted imaging (DWI) parameters obtained from primary nasopharyngeal carcinoma (NPC) at initial presentation, that can predict patients at risk of distant metastases. One hundred and sixty-four patients underwent pretreatment magnetic resonance imaging and DWI. The apparent diffusion coefficient (ADC)(mean), ADC(skewness), and ADC(kurtosis) were obtained by histogram analysis. Univariate and multivariate analyses of these ADC parameters together with primary volume (PV), nodal volume (NV), T stage, N stage and presence of locoregional relapse (LRR) were compared between patients with distant metastases (DM+) and patients without distant metastases (DM-)at 5 years using logistic regression. Twenty-eight out of 164 patients (17.1 %) were DM+(2.5-60 months) and 136/164 patients were DM-(61.2-119.4 months). Compared to DMpatients, the primary tumour of DM+ patients showed significantly lower ADC(skewness) (ADC values with the greatest frequency were higher) (p = 0.041), and higher PV (p = 0.022), NV (p < 0.01), T stage (p = 0.023), N stage (p < 0.01) and LRR (p < 0.01). On multivariate analysis the ADC(skewness) was no longer significant (p = 0.120) and only NV and LRR were independent predictors for DM+ (p = 0.023 and 0.021, respectively). DWI showed that compared to DM-patients, DM+ patients had a significantly lower primary tumour ADC(skewness), but at initial presentation NV was the only independent predictor of DM.