Abstract
BACKGROUND: Early tumor shrinkage (ETS) is a superior parameter for assessing treatment responses. Our study hypothesized that an ETS with an optimal cut-off value was an imaging biomarker for advanced esophageal squamous cell carcinoma (ESCC) treated with first-line immunotherapy. METHODS: We retrospectively enrolled 129 patients with unresectable locally advanced ESCC treated with first-line immunotherapy between 2019 and 2021. ETS was defined as the relative change in the longest diameters at the first evaluation compared with that at baseline. Multivariate analyses were conducted to identify the significant prognostic variables in progression-free survival (PFS) and overall survival (OS). RESULTS: The median value of ETS was 29.5%. An ETS with a 10% cut-off value was statistically significantly associated with PFS in the univariate analysis [hazard ratio (HR): 2.26; 95% confidence interval (CI): 1.21-4.24; P=0.009]. Besides, in the univariate analysis, the longest diameter, maximum invasive depth, central necrosis on enhanced computed tomography, enhanced pattern, and ETS values were statistically significant predictive factors for OS. In the multivariate analysis, the maximum invasive depth and ETS with a 10% cut-off value were independently predictive factors for OS (HR: 0.22; 95% CI: 0.09-0.52; P=0.001, HR: 2.93; 95% CI: 1.41-6.06; P=0.004). CONCLUSIONS: ETS is associated with survival outcomes in patients with advanced ESCC treated with immunotherapy. Early tumor size shrinkage of at least 10% can be regarded as a promising biomarker predictor for PFS and OS. ETS supports clinical decisions by identifying patients who can benefit from immunotherapy.