The incidence and management of immune checkpoint inhibitor-associated colitis and hepatitis.

Introduction: Immunotherapy is an increasingly important component of care in the management of several advanced malignancies, including metastatic melanoma and non-small cell lung cancer. Immune-mediated adverse events to therapy involving the gastrointestinal tract have been described, namely, autoimmune colitis and hepatitis. We aimed to evaluate the incidence, risk factors, and management of the gastrointestinal-related autoimmune side effects of checkpoint inhibitor therapy. Method(s): We conducted a retrospective audit of the files of all patients who received checkpoint inhibitor therapy at a major tertiary referral center from January 1, 2015, to June 1, 2017. We focused on the cytotoxic T-lym-phocyte-associated antigen 4 (CTLA-4) inhibitor ipilimumab and the programmed cell death 1 (PD-1) inhibitors nivolumab and pembrolizumab. We analyzed the data in two groups: patients who developed any autoimmune complications while being treated with checkpoint inhibitor therapy and patients who did not. We assessed for differences in pre-existing autoimmune comorbidities and liver function test results over a 16-week period from commencement of their therapy. We then performed an in-depth review of the management of the patients who developed autoimmune colitis and hepatitis. Result(s): We identified 56 patients receiving checkpoint inhibitor ther-apy, of whom 45 patients (80.4%) received nivolumab, seven (12.5%) received ipilimumab, and one (1.8%) received pembrolizumab. Three patients received both nivolumab and ipilimumab (5.4%). A total of 14/56 patients (33%) developed an autoimmune-related side effect. Of these 14 patients, four (28.6%) developed autoimmune colitis and one (7.1%) developed autoimmune hepatitis. The other common autoim-mune complications were hyperthyroidism (2, 14.3%), pneumonitis (2, 14.3%), and hypophysitis (2, 14.3%). There was no statistically significant difference between the two groups at baseline with respect to age, sex, or ethnicity. B