Complete remission of unresectable advanced esophageal squamous cell carcinoma following nivolumab immunotherapy after chemoradiotherapy: a case report

A 65-year-old man presented with dysphagia and was diagnosed with advanced thoracic esophageal squamous cell carcinoma (ESCC, cStage III, cT3N2M0). Initial treatment included three courses of preoperative chemotherapy with the DCF regimen. However, computed tomography (CT) showed tumor progression, leading to esophageal obstruction at the level of the tracheal bifurcation. The patient subsequently underwent chemoradiotherapy (CRT) combining the DCF regimen with radiotherapy (59.4 Gy). While CRT resulted in tumor shrinkage and reduced lymph node metastasis, residual target lesions persisted. As second-line therapy, nivolumab (240 mg/body, biweekly) was initiated. The treatment was well tolerated, with no significant adverse events. After 36 courses of nivolumab, complete response (CR) of both the primary tumor and metastatic lymph nodes was confirmed through CT, PET-CT, and upper gastrointestinal endoscopy. The patient has remained recurrence-free, with no evidence of new metastasis, and continues to maintain favorable clinical progress. A literature review identified only eight cases of CR achieved with nivolumab for advanced esophageal cancer, with only two involving ESCC, both in cases of recurrence after surgery or CRT. This is the first reported case of CR achieved with nivolumab in unresectable advanced ESCC. Despite PD-L1 expression being below 1%, nivolumab elicited a robust antitumor immune response. This case highlights the potential of immunotherapy, even in cases with low PD-L1 expression, for advanced ESCC.