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How should we diagnose and manage checkpoint inhibitor-associated colitis?

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Common endoscopic and histologic features

Once infection is ruled out, colonoscopy should be considered if symptoms persist or are severe. Colonoscopy with biopsy remains the gold standard for diagnosis, and it is also helpful in assessing severity of mucosal inflammation and monitoring response to medical treatment.

Table 2 lists common endoscopic and histologic features of ICI-mediated colitis; however, none of them is specific for this disease.

Common endoscopic features are loss of vascular pattern, edema, friability, spontaneous bleeding, and deep ulcerations.12 A recent study suggested that colonic ulcerations predict a steroid-refractory course in patients with immune-mediated colitis.4

Histologic features of immune checkpoint inhibitor-associated colitis

Figure 2. Histologic features of immune checkpoint inhibitor-associated colitis. High-resolution images of the colon showing normal histopathology (A), and colonic mucosa with intraepithelial lymphocytosis and occasional apoptosis in crypt epithelium (B) (hematoxylin and eosin, × 200).

Histologically, ICI-associated colitis is characterized by both acute and chronic changes, including an increased number of neutrophils and lymphocytes in the epithelium and lamina propria, erosions, ulcers, crypt abscess, crypt apoptosis, crypt distortion, and even noncaseating granulomas.13 However, transmural disease is rare. Figure 2 compares the histopathologic features of ICI-associated colitis and a normal colon.


Computed tomography (CT) can also be useful for the diagnosis and measurement of severity.

Garcia-Neuer et al14 analyzed 303 patients with advanced melanoma who developed gastrointestinal symptoms while being treated with ipilimumab. Ninety-nine (33%) of them reported diarrhea during therapy, of whom 34 underwent both CT and colonoscopy with biopsy. CT was highly predictive of colitis on biopsy, with a positive predictive value of 96% and a negative likelihood ratio of 0.2.14


Supportive care may be enough when treating mild ICI-related colitis. This can include oral and intravenous hydration4 and an antidiarrheal drug such as loperamide in a low dose.

Corticosteroids. For moderate ICI-associated colitis with stool frequency of 4 or more per day, patients should be started on an oral corticosteroid such as prednisone 0.5 to 1 mg/kg per day. If symptoms do not improve within 72 hours of starting an oral corticosteroid, the patient should be admitted to the hospital for observation and escalation to higher doses or possibly intravenous corticosteroids.

Infliximab has been used in severe and steroid-refractory cases,13 although there has been concern about using anti-tumor necrosis factor (TNF) agents such as this in patients with malignancies, especially melanoma. Since melanoma can be very aggressive and anti-TNF agents may promote it, it is prudent to try not to use this class of agents.

Other biologic agents such as vedolizu­mab, a gut-specific anti-integrin agent, are safer, have theoretic advantages over anti-TNF agents, and can be considered in patients with steroid-dependent or steroid-refractory ICI-associated enterocolitis. A recent study suggested that 2 to 4 infusions of vedolizumab are adequate to achieve steroid-free remission.15 Results from 6 clinical trials of vedolizumab in 2,830 patients with Crohn disease or ulcerative colitis did not show any increased risk of serious infections or malignancies over placebo.16,17 A drawback is its slow onset of action.

Surgery is an option for patients with severe colitis refractory to intravenous corticosteroids or biological agents, as severe colitis carries a risk of significant morbidity and even death. The incidence of bowel perforation leading to colectomy or death in patients receiving ICI therapy is 0.5% to 1%.18,19

Fecal microbiota transplant was associated with mucosal healing after 1 month in a case report of ICI-associated colitis.9

Follow-up. In most patients, symptoms resolve with discontinuation of the ICI and brief use of corticosteroids or biological agents. Patients with recurrent or persistent symptoms while on long-term ICI therapy may need periodic endoscopic evaluation, especially if there are chronic structural changes on histologic study.

If patients have recurrent or persistent symptoms along with chronic inflammatory structural changes on histology, a sign of an inflammatory bowel diseaselike condition, long-term maintenance therapy with an anti-inflammatory or immunosuppressant agent may be considered. However, there is no consensus on the treatment of this condition. It can be treated in the same way as classic inflammatory bowel disease in the setting of concurrent or prior history of malignancy, especially melanoma. Certain agents used in inflammatory bowel disease such as methotrexate and vedolizumab carry a lower risk of malignancy than anti-TNF agents and can be considered. A multidisciplinary approach that includes an oncologist, gastroenterologist, infectious disease specialist, and colorectal surgeon is imperative.

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