Diagnostic utility of CT for suspected immune checkpoint inhibitor enterocolitis

Abstract

Background and aimsImmune checkpoint inhibitor (ICI) enterocolitis is a common immune-related adverse event and can be fatal, especially when not diagnosed and treated promptly. The current gold standard for diagnosis is endoscopy with biopsy, but CT scan is a possible alternative. The primary objective of this study is to identify the diagnostic performance of CT in the evaluation of ICI enterocolitis.MethodsWith institutional review board approval, we conducted a retrospective cohort study of patients who received ICI therapy between 2015 and 2019 across a healthcare system. Patients were included if they underwent both abdominal CT and endoscopy with biopsy within 3 days. The radiological and pathological diagnoses, as well as clinical characteristics, were extracted from the electronic medical record. We calculated the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of CT for diagnosing ICI enterocolitis when compared with tissue diagnosis.ResultsOf the 4474 patients screened, 138 met inclusion criteria. Most common tumor types were melanoma (37%) and lung cancer (19%). Seventy-four per cent were treated with antiprogrammed cell death (PD-1)/PD-L1 therapy. Thirty-nine per cent had signs of enterocolitis on CT scan and 58% had biopsy-proven ICI enterocolitis. Sensitivity and specificity of CT were 50% and 74%, respectively. PPV was 73% and NPV was 52%. Of those with confirmed ICI enterocolitis, 70% had grade 3 or higher symptoms, 91% received steroids and 40% received infliximab.ConclusionThe performance of CT scan for diagnosis of ICI enterocolitis is moderate to poor and does not replace endoscopy with biopsy.

Gastrointestinal mucosal toxicities from immune checkpoint inhibitors: Current understanding and future directions

“…Most ICI induced enterocolitis is diagnosed clinically based on typical symptoms and timing associated with the initiation of ICIs after excluding common infectious causes of diarrhea, rather than through endoscopic examination and biopsy 34 . Cross sectional imaging has relatively little use in evaluating typical presentations of gastrointestinal irAEs due to poor sensitivity and specificity 40 . Although expedient, clinical diagnoses do have disadvantages, approximately 20% of patients with suspected gastrointestinal irAEs have alternative etiologies for their symptoms, which can include unanticipated complications from their malignancy 33,34,38,41 .…”

Update on Immune Checkpoint Inhibitor Enterocolitis

“…Both computed tomography (CT) and magnetic resonance imaging (MRI) have been reviewed on retrospective analyses, and neither provide conclusive diagnostic capability. CT sensitivity and specificity are both low and widely variable (53–85% and 75–78%, respectively) [40 , 41] . This is due in part to the wide differential that is indistinguishable on imaging, including new malignancy, infection, ischemia, and bowel wall edema.…”

Immunotherapy-induced Colitis

“…In contrast, a larger and more recent study seeking to replicate these findings reported a lower positive predictive value of 73% and a higher negative predictive value of 52%. 73 CT imaging can also be used to evaluate for possible complications of ICI-induced colitis. Findings of pneumatosis, free air, and the presence of megacolon in a toxic appearing patient indicate life-threatening complications and allow for timely intervention and consideration of surgical consultation.…”