S5697 Double Whammy Toxicity: A Case of Simultaneous Immune Mediated Colitis and Hepatitis After Pembrolizumab Therapy in Metastatic Bladder Cancer

Introduction: Since the development of next-generation sequencing, immune checkpoint inhibitors (ICI) have become increasingly common for the treatment of various types of cancers. Despite its clinical benefits, ICI therapy has been highly associated with a broad multisystemic list of toxicities, several of which involve the liver and gastrointestinal tract. We present a case of a patient on ICI therapy who developed subsequent colitis and hepatitis and the management that unfolded. Case Description/Methods: A 66-year-old man with medical history of metastatic bladder cancer, on pembrolizumab, presents to the emergency department for 7 days of persistent diarrhea and generalized weakness. The patient was started on ICI therapy 10 days prior to presentation and had since then experienced multiple daily watery bowel movements despite making appropriate dietary changes. Additionally, liver function tests (LFTs) were also elevated with aspartate aminotransferase 153, alanine aminotransferase 135, alkaline phosphatase 293, all from normal range at baseline. Computed tomography (CT) imaging of abdomen was unremarkable, and diarrhea panel was negative. Fecal elastase and stool ova and parasite were negative as well. The patient underwent colonoscopy which showed normal appearing mucosa in descending and sigmoid colon. His symptoms and lab abnormalities were deemed to be secondary to recently initiated immunotherapy. Given significant abdominal symptoms and markedly elevated LFTs, pembrolizumab was discontinued by oncology team and he was started on intravenous methylprednisolone with subsequent symptomatic improvement and mild reduction in LFTs. Discussion: This case highlights the potential nuances of diagnosing and managing ICI colitis (ICIC) and ICI hepatitis (ICIH). Although the American Gastroenterological Association emphasizes the importance of tissue diagnosis in ICIC, it’s been reported that as many as 20-30% of patients with suspected ICIC have no mucosal inflammation on endoscopic biopsies. For both ICIC and ICIH, severity is graded is based on using the Common Terminology Criteria for Adverse Events (CTCAE) which dictates whether immunotherapy can be continued, held, or stopped and whether steroid therapy is warranted to reverse effects. Although managing both ICIC and ICIH may be challenging, it is important to consider multidisciplinary shared decisions between hepatology, gastroenterology, and oncology to develop an appropriate management plan for such patients.