不可切除食管鳞状细胞癌经 ICI 治疗获完全缓解一例

BACKGROUND/AIM: Immune checkpoint inhibitors (ICIs) combined with chemotherapy are standard first-line therapy for unresectable advanced esophageal squamous cell carcinoma (ESCC). Tumor-infiltrating lymphocytes (TILs) are known to influence the efficacy of ICIs; however, the role of regulatory T cells (Tregs) remains unclear. We report a rare case in which long-term complete response (CR) to chemo-immunotherapy was achieved despite abundant Treg infiltration. CASE REPORT: A 49-year-old woman diagnosed with clinical stage IVA ESCC received pembrolizumab combined with FP (5-fluorouracil and cisplatin) chemotherapy. After four cycles, a complete response was confirmed by endoscopy, biopsy, computed tomography (CT), and positron emission tomography-CT (PET-CT). Pembrolizumab monotherapy maintained CR for 24 months before disease progression occurred, treated successfully thereafter with paclitaxel. Pretreatment biopsy immunohistochemistry revealed abundant FoxP3-positive Treg infiltration, limited CD8-positive cytotoxic T lymphocytes, absence of PD-L1, minimal tumor-associated macrophages, and high expression of HLA class I molecules. CONCLUSION: Contrary to previous reports that associated high Treg infiltration with reduced efficacy of ICIs, our patient demonstrated exceptional long-term CR. Potential influencing factors include synergistic chemotherapy effects, altered Treg function, and minimal presence of tumor-associated macrophages. This case underscores the complexity of tumor microenvironment interactions and suggests further investigation into Treg biology in predicting ICI treatment outcomes in ESCC.