Characteristics, Treatment, and Outcome of Diverticulitis Related to Immune Checkpoint Inhibitors in Patients With Malignancies

Introduction: Immune checkpoint inhibitors (ICIs) are an efficacious treatment for various malignancies. In addition to immune related adverse events (irAEs), there is growing evidence that ICIs might induce colonic diverticulitis. The aim of this study was to assess the clinical spectrum and management of diverticulitis among cancer patients after ICI treatment. Methods: A retrospective chart review was conducted on cancer patients who were exposed to ICIs between January 2010 and June 2020. Patients were divided into two groups: those who developed diverticulitis after ICI treatment (cases) and those who had diverticulitis before ICI treatment (controls). Patient clinical characters, treatment, and outcomes were compared between the two groups. Results: Among 502 cancer patients with a diagnosis of diverticulitis in the study window, 77 eligible patients were included in our final analysis where-in: 63 patients with a diverticulitis event after ICI and 14 as controls with diverticulitis only before ICI. Among 63 cases after ICI exposure, 46 had an initial episode, and 17 had recurrent episodes from pre-ICI era. Diverticulitis occurred after a median of 129 days (range: 32-277) after ICI initiation with anti-PD1/L1 monotherapy more frequently (75%). Clinical characteristics overlapped with traditional acute diverticulitis, with 93% of patients achieving symptom resolution with oral antibiotics alone. Diverticulitis complication rate in this ICI cohort is higher than traditional diverticulitis (23.8% vs 12%). Those with complicated ICI related diverticulitis more frequently needed hospitalization (87% vs 48%, P=0.015) and surgery/interventional radiology procedures (27% vs 0%, P=0.002), and had worse overall survival (P=0.022). Regarding recurrence after the first diverticulitis episode post ICI therapy, history of diverticulitis does not appear to contribute to more severe disease course. Immunosuppressants (e.g., corticosteroids) were rarely required unless concurrent ICI colitis was identified. Conclusion: Diverticulitis appeared to be more frequent after ICI therapy, particularly anti-PD-1/L1 therapy. Clinical presentation, evaluation, and management is similar to traditional diverticulitis, although it has higher complication rates requiring surgical intervention and impairing overall survival.