Introduction: Immune checkpoint inhibitors (ICPI) are increasingly becoming a standard oncological therapy. In addition to the intended anti-tumoral immune response, autoimmune effects such as colitis are observed.

Methods: Multicentre retrospective colitis case series in patients undergoing ICPI treatment. The substance used, duration to onset of colitis and severity of symptoms were evaluated. Diarrhea was described using a scale from G1(mild) to G5 (death).

Results: Between 2/2015 and 12/2017, 31 cases of ICPI induced colitis were documented. Twenty-one (68%) were male and 10 (32%) female. Median age was 62 years (24-88). Colitis was diagnosed after a median of 49 days (12-772) and after 3 cycles (1-23). Distribution of diarrhea severity was: G1:8 patients (32%), G2:12(38%), G3:11(34%), G4 or G5 were not reported. Twenty-six of 32 patients underwent colonoscopy. Affected intestinal segments were: rectum in 17 patients (65.4%), Sigmoid colon 16 (61.5%), left colon 11 (42.3%), ascending colon 2 (7.7%), pancolitis 1 (3.9%) and ileum 1 (3.9%). Prednisone or infliximab (IFX) were used for therapy. In group G1 3/8 (38%) received prednisone, 0 IFX; G2 9/12 (75%) prednisone, 0 IFX; G3 10/11 (91%) prednisone, 2 (18%) IFX.

Conclusion: ICPI-triggered enteritis is a new entity of autoimmune inflammatory bowel disease, which mostly affects the colon. Symptoms usually start after 2-3 cycles but can also arise after more than one year of therapy. The clinical course is usually mild to moderate and treatment with steroids is mostly sufficient.