Characteristics, treatment, and outcome of diverticulitis after immune checkpoint inhibitor treatment in patients with malignancies

Purpose: Immune checkpoint inhibitors (ICIs) are efficacious for treating various malignancies. In addition to immune-related adverse events (irAEs), growing evidence suggests that ICIs might also be associated with diverticulitis. We aim to assess the clinical presentations and management of colonic diverticulitis among cancer patients after ICI treatment. Methods: A retrospective study was conducted on ICI-treated adult cancer patients between 01/2010 and 06/2020. Patients were grouped based on when diverticulitis developed relative to ICI treatment, either before (controls) or after (cases). Patient clinical characters, treatment, and outcomes were compared between both groups. Results: 77 eligible patients were included: 63 patients developed diverticulitis after ICI exposure (46 had initial episode after ICI exposure, 17 had a history of diverticulitis prior then recurred after ICI exposure), and 14 had diverticulitis before ICI exposure. Diverticulitis occurred after a median of 129 days after ICI initiation. Clinical characteristics overlapped with traditional diverticulitis. 93% of patients had symptom resolution after treatment, while 23.8% experienced complications. These patients exhibited higher rates of hospitalization (87% vs 48%, P = 0.015) and surgery/interventional radiology procedures (27% vs 0, P = 0.002), and worse overall survival (P = 0.022). History of diverticulitis was not associated with a more severe disease course. Immunosuppressants (e.g., corticosteroids) were rarely required unless for concurrent ICI-mediated colitis. Conclusion: Colonic diverticulitis can occur after ICI therapy at very low incidence (0.5%). Its clinical presentation, evaluation, and management are similar to traditional diverticulitis, but associated with higher complication rates requiring surgical intervention and has lower overall survival.