The Role of Interleukin-6 as a Predictive Biomarker of Clinical Response to Biologic Therapy in Patients with Inflammatory Bowel Disease

This study aimed to evaluate whether serum levels of interleukin-6 (IL-6) can predict the clinical response to biologic therapy after 12 months of treatment in patients with inflammatory bowel disease (IBD). This was a prospective cohort study included 41 consecutive patients with IBD (23 ulcerative colitis, 18 Crohn’s disease) who were eligible for biologic therapy. Serum IL-6 levels were measured prior to initiating biologic treatment (T0) and after 10 weeks of therapy (T1). Clinical response after 12 months of treatment was defined as a reduction of ≥3 points in the Harvey–Bradshaw Index score or a reduction of ≥2 points in the partial Mayo score, in the absence of corticosteroid therapy. Receiver operating characteristic (ROC) curve analysis was used to assess the ability of IL-6 and to discriminate between responders and non-responders. Diagnostic accuracy was evaluated using the area under the curve (AUC). In the overall cohort, a baseline IL-6 level of ≥0.629 pg/mL and a decrease in IL-6 by ≥0.086 pg/mL within the first 10 weeks of treatment were predictive of clinical response (AUC = 0.745, sensitivity = 66.7%, specificity = 81.8%, P = 0.011; AUC = 0.821, sensitivity = 76.7%, specificity = 81.8%, P = 0.002, respectively). In patients with ulcerative colitis, a baseline IL-6 level of ≥0.629 pg/mL and a decrease in IL-6 by ≥0.115 pg/mL within the first 10 weeks of therapy predicted clinical response (AUC = 0.816, sensitivity = 73.3%, specificity = 87.5%, P = 0.015; AUC = 0.758, sensitivity = 73.3%, specificity = 75%, P = 0.035, respectively). In patients with Crohn’s disease, a decrease in IL-6 by ≥0.086 pg/mL within the first 10 weeks of treatment predicted clinical response (AUC = 0.933, sensitivity = 80%, specificity = 100%, P = 0.045). This study highlights the potential clinical role of serum IL-6 in predicting clinical response among IBD patients treated with biologic therapy.