S3859 Capecitabine Plus Oxaliplatin Induced Enterocolitis

Introduction: Diarrhea in an immunosuppressed host is a syndrome that carries a broad differential diagnosis. The differential is further broadened by medications that affect the immune response, such as chemotherapy and immune checkpoint inhibitors (ICI). We present a case of chemotherapy-induced enteritis due to capecitabine plus oxaliplatin (CAPOX). Case Description/Methods: A 76-year-old man with recurrent, metastatic esophageal squamous cell carcinoma presented to the hospital with fever and diarrhea. Two weeks prior, he was started on palliative chemotherapy with oxaliplatin, capecitabine, and pembrolizumab. Shortly thereafter, he developed abdominal pain followed by multiple episodes of watery, non-bloody diarrhea. Home medications included losartan. On presentation, he was febrile and hypotensive. Laboratory analysis showed leukopenia, neutrophilia, and 30% bands. Computed tomography of the abdomen and pelvis showed diffuse bowel wall edema and mucosal enhancement consistent with enteritis. Gastrointestinal pathogen stool PCR testing, including C. difficile, was negative. The patient was started on broad spectrum antibiotics and gastroenterology was consulted. Enteroscopy and colonoscopy were performed. Diffusely congested, friable, and bleeding mucosa was found in the jejunum and ileum. Congested mucosa was found in the entire colon. Biopsies were obtained. While awaiting these results, the patient was started on 1 mg/kg methylprednisone for empiric treatment of ICI enterocolitis. Biopsy results were more consistent with chemotherapy-induced enterocolitis. Thus, a diagnosis of CAPOX induced enterocolitis was made. Steroids were discontinued and supportive care was initiated. The patient subsequently developed acute respiratory distress syndrome secondary to influenza pneumonia. He died in the intensive care unit. Discussion: Our patient with fever and diarrhea was diagnosed with CAPOX induced enterocolitis after a workup ruled out common infectious entities and ICI colitis. Patients taking immune check point inhibitors have a high incidence of colitis which often responds to steroids and anti-tumor necrosis factor agents. Enterocolitis due to CAPOX is rare and associated with concurrent angiotensin II receptor blocker use. Treatment is generally supportive. In patients with more severe disease, endoscopic evaluation and mucosal biopsies are essential for determining the diagnosis to avoid further harm from unnecessary additional immunosuppression with steroids.