Diagnostic comparison of CT scans and colonoscopy for immune-related colitis in ipilimumab-treated advanced melanoma patients

Colitis can be a life-threatening toxicity for patients treated with immune checkpoint blockade antibodies. With the anticipated widespread use of these reagents, the timely and accurate diagnosis of immune-related colitis becomes increasingly important. To better understand the clinical presentation of colitis from ipilimumab and to assess the use of CT scans of the abdomen/pelvis as a diagnostic tool, we retrospectively analyzed patients with advanced melanoma who received ipilimumab at our institution. Ninety nine (33%) of 303 patients developed diarrhea during therapy, and 46 patients (15%) received corticosteroids for colitis. Of the patients with diarrhea, 48 (48%) underwent colonoscopy and 46 (46%) underwent both CT and colonoscopy. In the 34 patients (34%) with a CT and biopsy, CT was highly predictive of colitis on biopsy (positive predictive value 96%), and the absence of CT findings was predictive of a negative biopsy (negative likelihood ratio 0.2). In patients who had symptoms and CT evaluation, CT was highly predictive of the need for steroids to reach resolution of symptoms (positive predictive value 92%, positive likelihood ratio 7.3). We conclude that CT is a fast, reliable, and noninvasive mode of diagnosing colitis, whereas colonoscopy and biopsy may not be needed to establish that diagnosis.