Prognostic Value of Lymph Node-To-Primary Tumor Standardized Uptake Value Ratio in Esophageal Squamous Cell Carcinoma Treated with Definitive Chemoradiotherapy.

We aimed to investigate the prognostic value of the relative maximum standardized uptake value (SUV) of metastatic lymph node (LN) compared with that of primary tumor (SUVLN / SUVTumor) based on a pretreatment [18F]-FDG PET/CT scan in patients with clinically node-positive esophageal squamous cell carcinoma (cN+ ESCC) treated with definitive chemoradiotherapy (dCRT). We retrospectively evaluated cN+ ESCC patients who underwent a PET/CT scan before dCRT. Time-dependent receiver operating characteristics analysis was performed to identify the optimal cutoff value for SUVLN / SUVTumor. Prognostic influences of SUVLN / SUVTumor on distant metastasis-free survival (DMFS) and overall survival (OS) were evaluated using the Kaplan-Meier method and log-rank test for univariate analysis and Cox's proportional hazards regression model for multivariate analysis. We identified 112 patients with newly diagnosed cN+ ESCC. After a median follow-up of 32.0 months, 50 (44.6%) patients had distant failure and 84 (75.0%) patients died. Patients with high SUVLN / SUVTumor (≥ 0.39) experienced worse outcomes than low SUVLN / SUVTumor (< 0.39) (two-year DMFS: 26% vs. 70%, p < 0.001; two-year OS: 21% vs. 48%, p = 0.001). Multivariate analysis showed that SUVLN / SUVTumor was an independent prognostic factor for both DMFS (adjusted HR 2.24, 95% CI 1.34-3.75, p = 0.002) and OS (adjusted HR 1.61, 95% CI 1.03-2.53, p = 0.037). Pretreatment of SUVLN / SUVTumor is a simple and useful marker for prognosticating DMFS and OS in cN+ ESCC patients treated with dCRT, which may help in tailoring treatment and designing future clinical trials.