The Diagnostic Value Of ¹⁸F-FDG PET/CT Imaging In Detection Of Cervical Lymph Node Metastasis In Patients With Hypopharyngeal Cancer

Objective:To evaluate the diagnostic value of ¹⁸F-FDG PET/CT imaging in detection of cervical lymph node metastasis in patients with hypopharyngeal cancer and find the best diagnostic threshold from patient level and lymph node level.At the same time,we want to find the best diagnostic combination by combining metabolic indicator with morphological indicator.Methods:A total 0f 36 patients?23 males,11females?with hypopharyngeal cancer who underwent preoperative PET/CT examination and Neck Contrast enhancement ct?CE-CT?from January 2014 to December 2018 were enrolled in this retrospective study.Combined the results with pathology and clinical follow-up results,The sensitivity,specificity,accuracy,positive predictive value?PPV?and negative predictive value?NPV?of ¹⁸F-FDG PET/CT and CE-CT in cervical lymph node metastasis of hypopharyngeal carcinoma were compared by Fisher exact test.The lymph nodes matching the surgical records and pathological findings were selected from the PET/CT images,the long diameter,short diameter and SUVmax of lymph nodes on axial images were recorded.Pathological diagnosis was used as the gold standard,ROC curve was drawn to determine the optimal cutoff value and to assess the sensitivity,specificity,and accuracy.and evaluate the diagnostic efficacy of different indicator on lymph node metastasis.At the same time,the SUVmax threshold of the ipsilateral and contralateral lymph node metastasis of the primary lesion was diagnosed by ¹⁸F-FDG PET/CT through ROC and the diagnostic efficacy of the two was analyzed.Results:On a patient basis,the sensitivity,specificity,accuracy,positive predictive value and negative predictive value of 18F-FDG PET/CT in the diagnosis of cervical lymph node metastasis were 92.3%,70.0%,86.1%,88.9%,and 77.8%,respectively.The sensitivity,specificity,accuracy,positive predictive value and negative predictive value of CT lymph node metastasis in the diagnosis of pharyngeal carcinoma were 69.2%,40.0%,61.1%,75.0%,and 33.3%,respectively.By Fisher's exact text analysis,there was no significant difference in the sensitivity of PET/CT and CE-CT for regional lymph node metastasis of hypopharyngeal carcinoma,and the specificity and accuracy were significantly different.A total of 741 lymph nodes were resected,213 lymph nodes?62 Metastatic lymph nodes?MLN?and 151non—metastatic lymph nodes?NMLN??were matched with those on PET/CT images.The long diameter,short diameter and SUVmax of metastatic lymph nodes were 15.2±3.6 mm,7.4±2.2 mm,and 6.55±3.28,respectively.The long diameter,short diameter and SUVmax of non-metastatic lymph nodes were9.8±2.4 mm,4.7±1.6mm,and 1.35±1.47,respectively.The ROC of the long diameter,short diameter and SUVmax values of the lymph nodes were plotted,and the AUC values were 0.961,0.882,and 0.880.The optimal thresholds for diagnosing lymph node metastasis were:3.28?SUVmax?,12.2 mm?long diameter?,and 5.8 mm?short diameter?.The sensitivity,specificity,and accuracy of each threshold were90.2%,70.4%and 76.3%?sensitivity?,92.0%?84.8%and 84.0%?specificity?,91.5%?81.5%and 82.7%?accuracy?.With SUVmax?2.5 as the diagnostic standard,the sensitivity,specificity and accuracy were 96.7%?78.0%and 85.4%,respectively.When we use SUVmax?1.64 or short diameter?5.8mm as the diagnostic criteria for lymph node metastasis,the sensitivity,specificity and accuracy are 95.2%?86.8%and89.2%,respectively.The SUVmax of the ipsilateral metastatic lymph nodes was 7.42±3.84,and the contralateral side was 4.03±3.61.The difference was statistically significant?P=0.026?.The optimal threshold for the calculated lymph node metastasis was 4.35.The corresponding sensitivity,specificity,and accuracy were 80.9%,97.8%,and93.5%,respectively.The optimal threshold for contralateral lymph node metastasis was 2.44,corresponding sensitivity.Specificity and accuracy were:53.3%,84.7%,78.4%.Conclusion:1.In patients,18F-FDG PET/CT is superior to enhanced CT in the diagnosis of cervical lymph node metastasis of hypopharyngeal carcinoma.2.For lymph node level,¹⁸F-FDG PET/CT has a high diagnostic value for cervical lymph node metastasis of hypopharyngeal carcinoma.Compared with the long diameter?12.2mm and the short diameter?5.8mm,he best diagnostic value could be obtained if SUVmax?3.28 is considered as the diagnostic standard for lymph node metastasis.3.When the 18F-FDG PET/CT diagnosis of ipsilateral lymph node metastasis of primary pharyngeal carcinoma,the diagnostic threshold of SUVmax was 4.35;when the contralateral lymph node metastasis was diagnosed,the diagnostic threshold of SUVmax was 2.44.¹⁸F-FDG PET/CT predicts the high value of lymph node metastasis in the ipsilateral neck of the pharyngeal carcinoma,but it is less sensitive to the contralateral cervical lymph node metastasis.