Evaluation of detectability and diagnostic capability for neck lymphnode metastasis from head and neck cancer using C-11 methionine PET/CT

PURPOSE : We performed C-11 methionine PET/CT(MET-PET/CT) for patients with head and neck cancer and evaluated detectability and diagnostic capability for neck lymphnode metastasis. METHOD AND MATERIALS : Ninety-three patients with proven head and neck cancer admitted in our hospital for carbon ion rediotherapy were studied with MET-PET/CT before treatment. We found out 32 patients with any nodular accumulation in neck region from these patients. There were 47 nodules,suspicious candidate for lymph node metastasis.There were 12 malignant melanoma, 6 squamous cell carcinoma, 4 adenocarcinoma, 4 adenoid cystic carcinoma and 6 other carcinomas. We evaluated diagnostic characetenistics such as diagnostic indexes and ROC curve analysis.We use semi-quantitative parameter TNR,tumor to normal tissue ratio,for nodule activity.We analyzed the relation ship between TNR and noduls size,the CT diagnosis result using size critenia for lymph node metastasis and the clinical diagnosis result from long term follow up,respectively. RESULTS : Mean TNR of all nodules was 2.3(range:1.2-4.5)and mean nodule size was 8.6 mm(range:4.7-17.7mm).Correlation coefficient was 0.54, weekly correlated, between neck nodule activity and size. We classified nodules according to CT size into two groups. There were 9 nodules greater than 10 mm, the group diagnosed as metastasis, 38 nodules less than 10 mm in diameter. There was statistically significant dfference in nodule TNR between the two groups (p=0.001). Patients were followed for 6 to 36 months (mean: 14.3 months) and 20 nodules were diagnosed as metastasis. When we use CT size criteria or TNR (cutoff value 2.17), sensitivity, specificity and accuracy were 77.7%, 65.8% and 68.0% for CT size, 72.7%, 84.0% and 77.7% for TNR, respectively. Specificity and accuracy of the result using TNR value were superior to that of CT size criteria. From ROC curve analysis, Az value was 0.80. CONCLUSION : MET-PET/CT can be used as a valuable tool for assessing lymph node metastasis in patients with head and neck cancer, and it can diagnose neck metastasis more accurately than CT size criteria.92nd Scientific Assembly and Annual Meetin