Immunochemotherapy ± Salvage Chemoradiation for Local Recurrence of Esophageal Squamous Cell Carcinoma After Definitive Chemoradiotherapy

79 patients will receive treatment with a PD-1 inhibitor (sintilimab or camrelizumab 200mg, d1, q3w) combined with monotherapy chemotherapy (paclitaxel 175mg/m2 or docetaxel 75mg/m2 or irinotecan 270mg/m2, d1, q3w) for 4 cycles, followed by a 2-year maintenance treatment with PD-1 inhibitors. During this period, patients diagnosed with esophageal wall thickening and identified as having progressive disease (PD) have the option to undergo salvage radiotherapy (45-50.4 Gy/25-28/F/5-5.5 weeks) in conjunction with a dual-agent chemotherapy (paclitaxel 50 mg/m2, d1 + carboplatin AUC 2, d1, qw) for 5 cycles.