Radiotherapy Combined With Immunochemotherapy in Metastatic Esophageal Squamous Cell Carcinoma

In metastatic esophageal squamous cell carcinoma (ESCC), radiotherapy is often administered for palliative purposes to alleviate dysphagia. Recent studies suggest that combining radiotherapy with immunotherapy may have a synergistic effect on treatment outcomes. This study aims to investigate the efficacy and safety of adding Low-Dose Radiotherapy (LDRT) combined with Conventionally Fractionated Radiotherapy (CFRT) to first-line immunochemotherapy. Study Design:The protocol follows a sequential two-phase design: 1. Phase IIa (Safety Run-in / Pilot Phase):An initial cohort of approximately 20-25 patients will receive the experimental regimen (LDRT + CFRT + Immunochemotherapy) in a single-arm setting. The primary objective of this phase is to evaluate safety and feasibility. Safety Stopping Rule: A strict stopping rule is defined for the transition to the randomized phase. If 2 or more patients in the run-in cohort experience treatment-related death (Grade 5 Treatment-Related Adverse Events), the study will be terminated and will not proceed to Phase IIb. 2. Phase IIb (Randomized Controlled Phase):Upon confirmation that the safety criteria are met (i.e., \< 2 treatment-related deaths and acceptable toxicity profile), subsequent patients will be randomly assigned (1:1) to: Arm A (Experimental): PD-1 inhibitor plus chemotherapy (paclitaxel and platinum regimen) combined with LDRT and CFRT. Arm B (Control): PD-1 inhibitor plus chemotherapy alone. Primary Endpoint:The primary endpoint for the randomized phase is median progression-free survival (PFS).