Case Report: Successful treatment of mismatch repair-deficient cervical esophageal adenocarcinoma with immune checkpoint inhibition

Cervical (upper) esophageal adenocarcinoma is an extremely rare, aggressive, and biologically distinct subtype of esophageal cancer, with few cases reported in literature. As such, pathophysiology and treatment approaches remain poorly understood. We report a case of a 39-year-old male diagnosed with a locally advanced, unresectable, MMR-deficient cervical esophageal adenocarcinoma driven by double somatic mutation of the MLH1 gene. He was treated with pseudocurative intent treatment through combining standard of care (chemotherapy and immunotherapy) with high-dose radiation therapy. The patient achieved complete remission with no evidence of disease recurrence over three years after initial diagnosis. This case highlights the complex decision making that is involved in the treatment of rare cancers for which data from large randomized controlled trials are not available, and the importance of integrating trial data, tumor pathogenesis, biomarkers, and patient preferences.