Strategies to Optimize Anti-tumor Necrosis Factor Therapy for Perianal Fistulizing Crohn's Disease: A Systematic Review

Tumor necrosis factor (TNF) antagonists are considered the cornerstone therapy for fistulizing perianal Crohn's disease (PCD), yet a substantial proportion of patients fail to achieve healing. Therefore, we reviewed the evidence for strategies to enhance the efficacy of TNF antagonists for PCD. A systematic search of electronic databases through July 2018 was performed to identify studies that assessed the effectiveness of TNF antagonists combined with another medical or surgical intervention for PCD; or assessed the association between anti-TNF serum concentrations and fistula healing. Twelve studies compared anti-TNF therapy alone versus a combined approach: four with surgery, three with antibiotics, and five with immunomodulators. Only two studies, both with antibiotics, were rated high quality. The addition of antibiotics to anti-TNF therapy resulted in significantly higher rates of fistula response and healing in one study, and a trend toward reduction in fistula drainage in the other. Three of four studies found higher rates of fistula healing when surgery was combined with TNF antagonists. In contrast, one of five studies found a trend toward higher rates of fistula healing in patients treated concomitantly with immunomodulators. Five observational studies assessed the association between anti-TNF concentration and fistula healing. Higher infliximab serum concentrations were consistently associated with fistula healing. In conclusion, few high-quality studies assessing strategies to optimize anti-TNF therapy for PCD exist. Although antibiotics, possibly surgery, and higher serum infliximab concentrations appear to improve fistula healing, future prospective studies are needed to determine the optimal treatment strategy.