Diagnostic accuracy of diffusion-weighted MR imaging for nasopharyngeal carcinoma, head and neck lymphoma and squamous cell carcinoma at the primary site

Abstract

The feasibility of performing diffusion-weighted MRI (DWI) of primary undifferentiated nasopharyngeal carcinoma (NPC) has not been assessed and it is unknown whether the apparent diffusion coefficients (ADC) of primary NPC differs from that of lymphoma or squamous cell carcinoma (SCC) in the head and neck. One hundred patients with newly diagnosed NPC, head and neck lymphoma or SCC underwent echo-planar DWI. ADCs of primary tumours were compared by Kruskal-Wallis test and Mann-Whitney U tests with Bonferroni correction using p<0.05 and p<0.017 respectively to indicate statistical significance. The utility of ADC thresholds for discriminating tumour histology was evaluated by receiver operating characteristic analysis. DWI was successful in 45/65 with NPC, 5/7 with lymphoma and 26/28 with SCC. Mean ADC (+/-SD) of NPC, lymphoma and SCC were 0.98+/-0.161, 0.75+/-0.190, 1.14+/-0.196 (x10(-3)mm(2)/s) respectively which were significantly different (p<0.001-0.003). Optimized ADC thresholds of 0.779, 0.768 and 1.07(x10(-3)mm(2)/s) achieved maximal discriminatory accuracies of 100%, 93% and 70% for SCC/lymphoma, NPC/lymphoma, and SCC/NPC respectively. Echo-planar DWI is a feasible technique for investigating primary NPC although limited in a third of patients due to susceptibility artifacts around the skull base. While the overall ADC value of NPC is significantly different to that of SCC and lymphoma, on a case by case basis overlapping ADCs between these tumours limit its theoretical utility at this site. Nevertheless, DWI may still be useful clinically to distinguish NPC from nasopharyngeal lymphoma in populations with endemic NPC due to the relative rarity of nasopharyngeal SCC.