The value of 18F-FDG PET/CT in N staging nasopharyngeal carcinoma patients

Objective To investigate the value of 18F-FDG PET/CT in N staging nasopharyngeal carcinoma (NPC) patients compared with CT or MRI.Methods Sixty-two patients (48 males,14 females,median age 43 y) with NPC confirmed by biopsy were enrolled into this prospective study.All patients underwent CT or MRI as well as 18F-FDG PET/CT imaging 1 week before the radiotherapy and staging was based on AJCC 6th edition.The accuracies of the two imaging methods for N staging were evaluated by follow-up clinical results (≥6 months).Kappa and x2 tests were used to analyze the usefulness of 18F-FDG PET/CT imaging for N staging.Results All of the 62 patients (N0 =9,N1 =16,N2 =24,N3 =13) underwent imaging.In this patient-based analysis,the accuracy of 18F-FDG PET/CT imaging for N staging was 96.8％ (60/62) and Kappa was 0.955,which were 72.7％ (45/62) and 0.607 for CT or MRI.30.6％ (19/62) patients had discrepant results of N staging in PET/CT and CT or MRI.27.4％ (17/62)patients underwent changes in their N staging by PET/CT correctly.Of note,one patient's stage changed from N0 to N2 (radiotherapy to chemoradiotherapy) and another 16 patients had changes in the exposure doses for drawing GTV.The positive rate of PET/CT for retropharyngeal 1ymph node detection was 54.8％ (34/62),and the sensitivity,specificity and accuracy were 80.0％ (20/25),94.4％ (17/18) and 86.0％ (37/43).By comparing 43 patients that underwent MRI and PET/CT imaging,results were comparative in nodal detection:60,5％ (26/43) in MRI vs 55.8％ (24/43) in PET/CT (x2 =2.000,P ＞0.05).Conclusions 18F-FDG PET/CT imaging has higher accuracy for N staging in NPC than CT or MRI.It could also be more sensitive to retropharyngeal lymphadenopathy especially for small lymph nodes. Key words: Nasopharyngeal neoplasms; Tomography, emission-computed; Tomography, X-ray computed; Deoxyglucose