A Rare Case of Complete Remission in Metastatic Esophageal Squamous Cell Carcinoma: Potential Abscopal Effect of Combined Immunotherapy and Radiotherapy – A Case Report

Introduction: Esophageal squamous cell carcinoma (SCC) is an aggressive malignancy associated with a poor prognosis, even when managed with multimodal therapeutic approaches. Case Presentation: This case report describes a 38-year-old woman who developed metastatic esophageal SCC following prior optimal treatment for initially locoregional disease. Due to poor tolerance of neoadjuvant chemotherapy and programmed death-ligand 1 (PD-L1)/tumor proportion score (TPS) of 5%, palliative immunotherapy with ipilimumab and nivolumab was initiated. After nodal progression during dual immunotherapy, the addition of palliative local radiotherapy to an inguinal lymph node, delivering a total dose of 20 Gray (Gy)/25 Gy/35 Gy over 5 fractions, resulted in complete remission of the thoraco-abdominal metastases. Fifteen months after the administration of palliative radiotherapy, an oligopersistent cervical lymph node was treated with stereotactic radiotherapy (5 × 5 Gy/7 Gy = 25 Gy/35 Gy). More than 2 years following the diagnosis of metastatic disease, the patient remains without evidence of disease. Conclusion: This case demonstrates an excellent response to combined immunotherapy in advanced esophageal SCC, including a rare abscopal effect following short-course radiotherapy.