Background: Immune checkpoint inhibitors (ICIs) are efficacious in treating many advanced malignancies. However, drug induced colitis limits their use significantly. We present cases with chronic refractory ICI colitis requiring long term immunosuppressive therapy and favorable cancer outcomes. Methods: We identified 3 cases who developed ICI colitis and persisted for longer than 6 months requiring long term immunosuppressant therapy. The patients’ clinical data was collected. Results: All patients were male, with median age of 55. Two had melanoma, one urothelial cancer. All patients received PD-1(L)-1 agents with colitis onset about 3-6 months after ICI treatment. All patients were taken off ICI permanently due to colitis over a duration of 19-30 months (peak grade of 3). Endoscopy of all three were grossly unremarkable, with lymphocytic colitis on pathology in all three. Patient A’s colitis achieved clinical and histological remission after 5 doses of vedolizumab, however recurred after 9 months with biopsy proven recurrence. Current management is anti-diarrheal medication given mild symptom. Patient B had more aggressive disease, with first recurrence after 2 doses of infliximab and steroid, achieved initial histological remission after 3 doses of vedolizumab and 2 additional infliximab, then had 2^nd recurrence after 3 months. Fecal microbiota transplantation as compassionate treatment was not effective. Thereafter, patient was resumed on vedolizumab ever since with clinical remission. Last histology evaluation showed persistent lymphocytic colitis 30 months after initial diagnosis. The third case had initial histological remission after 3 doses of vedolizumab, followed by recurrence after 4 months, which triggered another 3 doses of vedolizumab, with persistent grade 3 diarrhea despite resolution of histological inflammation after total 6 doses of vedolizumab. Patient was subsequently treated with steroid and ustekinumab with clinical remission. At the end of follow up, all three patients have sustained cancer remission over 19-31 months. Conclusions: IMC is a common adverse event from ICI, and could progress to a chronic inflammatory condition that require long term treatment. Histological remission does not preclude future recurrence of colitis. Persistent toxicity could be a surrogate marker for enduring ICI effect which may be associated with favorable cancer outcome. Long term immunosuppression can be essential for refractory ICI colitis cases for clinical remission.