2299. Imaging Characteristics of Biopsy Proven Immune-Related Colitis in Patients Treated with PD-1 Inhibitors
Authors * Denotes Presenting Author
  1. Marta Braschi-Amirfarzan *; Lahey Health Medical Center
  2. Richard Thomas; Lahey Health Medical Center
  3. Jeremy Wortman; Lahey Health Medical Center
  4. Shilpa Grover; Brigham and Women Hospital
We aimed to evaluate the prevalence of individual radiographic features of colitis in patients treated with PD-1 inhibitors.

Materials and Methods:
This study included 62 patients with metastatic disease treated with PD-1 inhibitor monotherapy using pembrolizumab (34) or nivolumab (28) who developed biopsy proven colitis while on treatment, and had concomitant imaging, a baseline CT and at least one follow-up abdominal CT during therapy. Abdominal CTs were reviewed in consensus by two body radiologists to identify imaging features of colitis, which included fluid-filled colon, wall thickening, mucosal hyperemia and aft stranding, individually or in combination.

22 patients (35.5%) demonstrated all the four CT features of colitis in combination, at a mean of 5 weeks after starting PD-1 therapy. However, when imaging features were assessed individually, 45 patients (72%) demonstrated idiographic evidence of colitis, as follow: Bowel wall thickening in 42(67%), fluid-filled colon in 20 932%), fat stranding in 23 (37%) and mucosal hyperhancement in 37 (43%). 17 patients had no imaging features of colitis (27%). 18 patients had pancolitis, 16 with superimposed segmental complicated acute diverticulitis (SCAD), 8 SCAD only. All 8 patients with SCAD pattern had involvement of the sigmoid colon. Although all four imaging features of PD-1 inhibitor colitis are see in up to one third of patients, individual imaging features are seen in a much larger fraction, with colonic wall thickening being the most common. SCAD pattern always involves the sigmoid colon.

Given the widespread use of PD-1 inhibitors, radiologist should be aware of the imaging characteristics of PD-1 inhibitor colitis and assess for these features both individually and in combination.