F-18 FDG PET/CT contributes to more accurate detection of lymph nodal metastasis from actively proliferating esophageal squamous cell carcinoma

Purpose: Evaluating the status of disease progression is critical for planning a therapeutic strategy for esophageal cancer. In this regard, F-18 fluorodeoxyglucose-labeled positron emission tomography (PET) is one of the most useful diagnostic modalities. However, there is room to improve its diagnostic performance, such as distinguishing lymph nodal metastases from false positives. In this study, we examined the diagnostic accuracy of fluorodeoxyglucose PET accompanied by computed tomography imaging (PET/CT) to detect regional lymph nodal metastasis from esophageal squamous cell carcinoma (ESCC). Methods: A total of 102 patients diagnosed as ESCC were subjected to this study. These patients had a preoperative PET/CT examination to evaluate the existence of metastasis. The values of maximum standardized uptake value (SUV _max) in primary tumors and in metastasized lymph nodes were measured to analyze their relationship with various clinicopathologic characteristics including the status of tumor cell proliferation, which was assessed by immunohistochemistry for Ki-67. Results: The SUV _max of the primary tumor was positively correlated with tumor size and vessel invasion, and was positively related with the SUV _max of lymph nodal metastasis, especially in cases of poorly differentiated ESCC. The SUV _max of metastasized lymph nodes was higher in larger-sized metastasized lymph nodes, whereas the Ki-labeling index of lymph nodal metastasis was positively related with the SUV _max per unit area (SUV _max/mm ²). The diagnostic accuracy of PET/CT (87.3%) was higher than that of conventional CT scans (78.4%). Conclusions: The improved diagnostic accuracy of PET/CT can be explained by its ability to detect actively progressive metastasis at an early phase regardless of size.