[The values of MRI, CT, and PET-CT in detecting retropharyngeal lymph node metastasis of nasopharyngeal carcinoma]

Abstract

Background & objective: Three-dimensional conformal and intensity-modulated radiotherapy is the direction of developing radiotherapy for nasopharyngeal carcinoma (NPC). The accuracy of target area outlines is especially important. This study was to explore the clinical diagnostic values of magnetic resonance imaging (MRI), computed tomography (CT), and 18-F-fluorodeoxyglucose (FDG)-positron emission tomography (PET)-CT in detecting retropharyngeal lymph node metastasis of NPC, and to provide references to the plan of radiotherapy.

Methods: MRI, enhanced spiral CT, and PET-CT reports of the nasopharynx and whole neck of 87 naive NPC patients, histologically diagnosed and treated in Cancer Center of Sun Yat-sen University between Jan. 2003 and Apr. 2005, were analyzed. The detection rates of retropharyngeal lymph node metastasis were compared among MRI, CT and PET-CT using Chi-square test.

Results: Among the 174 parapharyngeal spaces of the 87 patients, the detection rates of retropharyngeal lymph node metastasis by MRI and CT were significantly higher than that by PET-CT (44.8% and 33.9% vs. 24.1%, P < 0.001 and P = 0.002). As compared with CT, MRI played an advantage in detecting retropharyngeal lymph node metastasis of NPC (P = 0.037). The minimal axial diameter of retropharyngeal lymph node was positively correlated to the standard uptake value (SUV) of PET-CT (r = 0.832, P <0.001).

Conclusions: MRI are better than CT and PET-CT in detecting retropharyngeal lymph node metastasis of NPC. The combination of MRI, CT, and PET-CT is useful for delineating targets accurately in 3-dimensional conformal intensity-modulated radiotherapy for NPC.