The role of fecal calprotectin in assessing response to advanced medical treatments for inflammatory bowel diseases: a review of the literature

Introduction: In the era of treat-to-target (T2T), there is an urgent need for surrogate non-invasive markers to monitor patients with inflammatory bowel diseases (IBD). Fecal calprotectin (FC), a non-invasive biomarker reflecting intestinal inflammation, holds potential for improving treatment monitoring. This narrative review aims to provide an overview of the role of FC in assessing responses to biological therapies and the new small molecules. Evidence acquisition: A comprehensive literature review was performed using major databases, including PubMed, Embase, Scopus, Cochrane Library, and Web of Science, to identify studies that assessed the performance of FC in predicting treatment responses to advanced therapies in both adult and pediatric IBD populations. Performance was specifically evaluated in terms of area under the curve (AUC) values. Evidence synthesis: Numerous studies demonstrated FC's association with treatment response to biologics and small molecules. While some studies reported strong predictive validity (AUC values up to 0.9), others demonstrated lower performance (AUC ranging from 0.6 to 0.9), depending on the specific outcomes assessed. Longitudinal monitoring of FC levels proved superior to single time point assessments. Pediatric patients with IBD showed similar FC patterns to adults. Conclusions: This review supports the use of FC to assess treatment response in patients with IBD, both in clinical research and clinical practice. Comprehensive prospective studies, randomized controlled trials (RCTs), and meta-analyses with data standardizations will enhance the FC's future clinical application in IBD management, supporting the T2T strategy while minimizing the need for invasive procedures.