Creeping fat is associated with transmural healing in patients with Crohn's disease receiving ustekinumab.

Objectives: We investigated whether body composition parameters assessed on baseline computed tomography enterography (CTE) could predict transmural healing (TH) in patients with Crohn's disease (CD) receiving Ustekinumab (UST).

Materials and methods: Adult patients with active CD treated with standard UST from August 2020 to August 2022 were enrolled. Body composition, including creeping fat (CF, mesenteric creeping fat index (MCFI) and fibrofatty proliferation score), skeletal muscle, visceral adipose, and subcutaneous adipose-related parameters were assessed on baseline CTE. Cox regression analysis was performed to identify independent predictors of TH.

Results: This study included 113 patients, and TH occurred in 26 (23. 0%) patients. The results of the univariable analysis indicated a statistically significant association of the presence of sarcopenia, higher MCFI score, and higher fibrofatty proliferation score with an increased failure rate of TH. We found no evidence that skeletal muscle index, subcutaneous adipose index, visceral adipose index, and visceral adipose/subcutaneous adipose area ratio were associated with TH. Multivariable analysis revealed that sarcopenia (Hazard ratio (HR): 0.35, 95% CI: 0.14-0.87, p = 0.023), MCFI score (HR: 0.67, 95% CI: 0.49-0.91, p = 0.010) and fibrofatty proliferation score (HR: 0.50, 95% CI: 0.29-0.85, p = 0.011) remained significant. MCFI score (χ²-df = 5.58) was the most critical factor for TH prediction, followed by fibrofatty proliferation score (χ²-df = 5.43) and sarcopenia (χ²-df = 4.12).

Conclusions: Among all the body composition parameters, MCFI and fibrofatty proliferation score assessed on baseline CTE were independently associated with TH, and they demonstrated greater predictive efficacy compared to sarcopenia.

Critical relevance statement: Creeping fat on baseline CTE was an important predictive factor for transmural healing in patients with Crohn's disease receiving Ustekinumab, which enables early risk stratification of patients and has potential implications for decision-making.

Key points: Identifying predictors of transmural healing may provide insight into earlier dose optimization to improve the rate of transmural healing. Higher creeping fat scores (mesenteric creeping fat index and fibrofatty proliferation) were independently associated with a lower rate of transmural healing. Mesenteric creeping fat index and fibrofatty proliferation score demonstrated greater predictive efficacy compared to sarcopenia.