Detection of Nasopharyngeal Carcinoma by MR Imaging: Diagnostic Accuracy of MRI Compared with Endoscopy and Endoscopic Biopsy Based on Long-Term Follow-Up

Abstract

Background and purpose: Our previous nasopharyngeal carcinoma detection study, comparing MR imaging, endoscopy, and endoscopic biopsy, showed that MR imaging is a highly sensitive test that identifies nasopharyngeal carcinomas missed by endoscopy. However, at the close of that study, patients without biopsy-proved nasopharyngeal carcinoma nevertheless had shown suspicious abnormalities on endoscopy and/or MR imaging. The aim of this study was to determine whether there were any patients with undiagnosed nasopharyngeal carcinoma by obtaining long-term follow-up and to use these data to re-evaluate the diagnostic performance of MR imaging.

Materials and methods: In the previous study, 246 patients referred to a hospital ear, nose, and throat clinic with suspected nasopharyngeal carcinoma, based on a wide range of clinical indications, had undergone MR imaging, endoscopy, and endoscopic biopsy, and 77 had biopsy-proved nasopharyngeal carcinoma. One hundred twenty-six of 169 patients without biopsy-proved nasopharyngeal carcinoma underwent re-examination of the nasopharynx after a minimum of 3 years, including 17 patients in whom a previous examination (MR imaging = 11; endoscopy = 7) had been positive for nasopharyngeal carcinoma, but the biopsy had been negative for it. Patients with nasopharyngeal carcinoma were identified by biopsy obtained in the previous and this follow-up study; patients without nasopharyngeal carcinoma were identified by the absence of a tumor on re-examination of the nasopharynx. The sensitivity and specificity of the previous investigations were updated and compared by using the Fisher exact test.

Results: One patient with a previous positive MR imaging finding was subsequently proved to have nasopharyngeal carcinoma. Nasopharyngeal carcinomas were not found in the remaining 125 patients at follow-up, and the previous positive findings for nasopharyngeal carcinoma on MR imaging and endoscopy were attributed to benign lymphoid hyperplasia. The diagnostic performances for the previous MR imaging, endoscopy, and endoscopic biopsy were 100%, 88%, and 94%, respectively, for sensitivity, and 92%, 94%, and 100%, respectively, for specificity; the differences between MR imaging and endoscopy were significant for sensitivity (P = .003) but not specificity (P = .617).

Conclusions: MR imaging detected the 12% of nasopharyngeal carcinomas that were endoscopically invisible, including 1 cancer that remained endoscopically occult for several years. Lymphoid hyperplasia reduced the specificity of MR imaging.

Fig 1.

Flow chart of the study design.

Fig 2.

Axial T1-weighted postcontrast MR imaging of a 48-year-old man with NPC (arrow). A, Note a small moderately contrast-enhancing NPC in the right pharyngeal recess on MR imaging at presentation (grade 4), which was not detected by endoscopy or endoscopic biopsy or at repeat biopsy targeted to the site of the MR imaging abnormality. B, Persistent NPC on MR imaging is seen at 31 months, but without a tumor on endoscopic examination. A further biopsy was declined. C, An increase in the size of the NPC on MR imaging at 43 months when the tumor was confirmed by endoscopy and biopsy.

Fig 3.

Axial T1-weighted postcontrast MR imaging of a 54-year-old man with lymphoid hyperplasia. MR imaging shows a smooth band with mild enhancement in the right side of the walls of the nasopharynx (arrows), extending from the adenoid (arrowhead), which is asymmetric in thickness compared with the left side and had been misdiagnosed as positive for NPC by MR imaging (grade 3).

Fig 4.

Axial T1-weighted postcontrast MR imaging of a 69-year-old man with benign lymphoid hyperplasia in the adenoid (arrows), which had been positive for NPC by endoscopy but was correctly diagnosed as benign by endoscopic biopsy and MR imaging on the basis of the symmetric alternating bands of marked and mild contrast enhancement causing a striped appearance to the enlarged adenoid (grade 2).