Prognostic Significance of 18F-fluorodeoxyglucose Positron Emission Tomography (FDG-PET)-Positive Lymph Nodes Following Neoadjuvant Chemotherapy and Surgery for Resectable Thoracic Esophageal Squamous Cell Carcinoma

Patients with resectable thoracic esophageal squamous cell cancer (TESCC) and positron emission tomography (PET)-positive lymph nodes (PET-N positive) are likely to have a parts per thousand yen3 pathological lymph node metastases (pLNMs) and show a higher rate of postoperative recurrence despite curative resection than PET-N-negative TESCC patients. We examined the prognostic significance of F-18-fluorodeoxyglucose uptake into lymph node metastases after neoadjuvant chemotherapy (NAC) for PET-N positive TESCC and aimed to propose the optimal NAC response criteria for these patients. Fifty-one patients with PET-N positive TESCC underwent two courses of NAC followed by surgery. Metabolic responses of primary tumors and LNs were prospectively evaluated and associations with clinicopathological data and patient survival assessed by univariate and multivariate analyses. After NAC, 21 patients were post-treatment (post-) PET-N positive and 30 post-PET-N negative. A significantly (p < 0.001) high proportion of the post-PET-N-negative group had a parts per thousand currency sign2 pLNMs than the post-PET-N positive group (86.7 vs. 28.6 %). The PET-N negative group also had a significantly lower distant metastasis rate (23.3 vs. 75.0 %) and higher 5-year relapse-free survival (RFS) rate (69.0 vs. 20.0 %). Univariate and multivariate Cox's proportional hazard regression analyses identified post-PET-N negative status as the only significant favorable predictive factor for low postoperative recurrence (p = 0.015) independent of the primary tumor response. PET-N negative status predicts a parts per thousand currency sign2 pLNMs and longer RFS in resectable TESCC patients even after NAC. Therefore, post-PET-N status, not the effects on the primary tumor, is a critical NAC treatment response criterion for evaluating prognosis and guiding subsequent treatment.