2582 Background: Colitis is a frequent toxicity of ICI therapy but there is paucity of data on risk factors. Specific serological markers and genetic polymorphisms have been associated with inflammatory bowel disease (IBD) (ulcerative colitis, Crohn’s disease). However, the prevalence of these markers in pts with ICI colitis is unknown. We performed a pilot study to determine the prevalence of IBD-associated genetic and serologic biomarkers in pts with ICI colitis. Methods: Cancer pts with histologically confirmed ICI enteritis/colitis and no history of IBD underwent commercial IBD panel testing. The panel included 4 genetic markers ( ATG16L1, NXK2–3, ECM1, STAT3), 8 serological markers (anti-A4-Fla2, anti-A4-FlaX, anti-CBir1, anti-OmpC, ASCAIgA, ASCA-IgG, pANCA, ANCA), and 5 inflammatory markers (vascular endothelial growth factor [VEGF], intracellular adhesion molecule 1[ICAM-1], vascular cell adhesion molecule 1 [VCAM-1], C-reactive protein, serum amyloid A [SAA]). Clinical testing on serum samples was performed by Prometheus Laboratories (San Diego, CA). Results: Of 15 cancer pts with biopsy confirmed ICI colitis, 10 (67%) were homozygous for 1 or more of 4 genetic markers. The remaining 5 pts were all heterozygous for two or more of the genetic markers. One or more serologic markers associated with IBD were elevated in 7/15 (47%) pts. Serum reactivity was noted for ASCA-IgA (1/15, 7%), ASCA-IgG (1/15, 7%), anti-OmpC (3/15, 20%), anti-CBR IgG (2/15, 13%), anti-A4-FlaX (1/15, 7%), and ANCA (2/15, 13%). One or more inflammatory markers were elevated in 13/15 (88%) pts. Elevations in VEGF, VCAM-1, ICAM-1, and SAA were noted in 2 (13%), 8 (53%), 8 (53%), and 11 (73%) pts, respectively. Only 6 (40%) pts had elevations in CRP levels despite the presence of active inflammation on biopsy. The IBD panel was reported as being consistent with Crohn’s disease in 2 pts, ulcerative colitis in 1 pt and inconclusive for type but consistent with IBD in 1 pt. Conclusions: In this pilot study, all patients with ICI colitis, were either homozygous or heterozygous for two or more high risk IBD alleles. If validated, such testing may prospectively identify pts at risk for developing ICI colitis.
Genetic Markers Predict Primary Non-Response and Durable Response To Anti-TNF Biologic Therapies in Crohn’s Disease