Detection of recurrent nasopharyngeal carcinoma: MR imaging versus CT.

PURPOSE: To compare the use of magnetic resonance (MR) imaging and computed tomography (CT) in detection of recurrent nasopharyngeal carcinoma. MATERIALS AND METHODS: Forty-five sets of CT and MR images were obtained in 34 patients. The images were placed in three categories: (a) clinically or radiologically abnormal findings in patients who underwent biopsy (n = 16), (b) clinically normal and radiologically borderline findings in patients who were followed up clinically and radiologically (n = 10), and (c) clinically and radiologically normal findings in patients who were monitored only clinically (n = 19). All images were read by two observers independently. RESULTS: There were nine positive and seven negative biopsy results. All patients in the latter two categories had normal findings at followup. CT had a sensitivity of 45% and 67% and a specificity of 64% and 70% for each of the two observers. MR imaging had a sensitivity of 56% (for both observers) and a specificity of 78% and 83%. The kappa test for interobserver concordance was 0.53 for CT and 0.66 for MR imaging. CONCLUSION: Both modalities have relatively low sensitivity and moderate specificity in detection of tumor recurrence and in distinguishing recurrence from post-radiation therapy changes.