Utility of major basic protein, eotaxin-3, and mast cell tryptase staining for prediction of response to topical steroid treatment in eosinophilic esophagitis: analysis of a randomized, double-blind, double dummy clinical trial.

Inflammatory factors in eosinophilic esophagitis (EoE), including major basic protein (MBP), eotaxin-3 (EOT3) and mast cell tryptase (TRP), may predict treatment response to topical corticosteroids (tCS). We aimed to determine whether baseline levels of these markers predict response to tCS for EoE. To do this, we analyzed data from a randomized trial comparing two topical steroids for treatment of newly diagnosed EoE (NCT02019758). A pretreatment esophageal biopsy was stained for MBP, EOT3, and TRP to quantify tissue biomarker levels (cells/mm2). Levels were compared between histologic responders (<15 eos/hpf) and nonresponders (the primary outcome), and endoscopic responders (EREFS<2) and nonresponders. Complete histologic response (<1 eos/hpf) was also assessed, and area under the receiver operator characteristic curve (AUC) was calculated. We also evaluated whether baseline staining predicted symptom relapse in the trial's off-treatment observation phase. Baseline samples were evaluable in 110/111 subjects who completed the randomized trial. MBP levels were higher in nonresponders (n = 36) than responders (704 vs. 373 cells/mm2; P = 0.007), but EOT3 and TRP levels were not statistically different. The combination of all three stains had an AUC of 0.66 to predict response. For complete histologic response, baseline TRP levels were higher in nonresponders (n = 69) than responders (370 vs. 268 mast cells/mm2; P = 0.01), with an AUC of 0.65. The AUC for endoscopic response was 0.68. Baseline staining did not predict symptom recurrence after remission. Pretreatment MBP, EOT3, and TRP levels were not strongly or consistently associated with histologic or endoscopic response to topical steroids. While elevated TRP levels may be associated with nonresponse compared with complete response, the magnitude and predictive utilities were modest. Novel methods for predicting steroid response are still required.