Treat-to-target, specifically transmural radiologic healing, is a potentially critical concept in Crohn's disease (CD) management algorithms. Currently, mucosal healing as assessed by endoscopic evaluation is the most utilised follow-up assessment for inflammatory bowel disease (IBD).¹ However, endoscopic techniques may be suboptimal for global intestinal disease interrogation due to “segmental skipping” and/or intramural disease.² Furthermore, there is not yet a globally accepted and validated definition of transmural healing or a multi-modality radiologic target.³

Various CD imaging tests have been assessed as potential prognostic tools. Magnetic resonance enterography (MRE) and computed tomography enterography can identify radiologic response with medical therapy, which has been linked to reductions in long-term risk of hospitalisation, surgery, and/or corticosteroid use.¹ An early (8 weeks) reduction (>18% decrease) in terminal ileal bowel wall thickness on intestinal ultrasound (IUS) has predicted endoscopic remission in children with CD, and IUS outperformed symptoms and C-reactive protein for this purpose.⁴ However, there is a paucity of data regarding the potential prognostic significance of follow-up individual MRE imaging parameters and scoring with the magnetic resonance index of activity (MaRIA).^{5, 6}

Fernández-Clotet et al. sought to explore this issue with a post hoc analysis of 89 patients (58 biologic-naïve) from a prospective longitudinal study at a tertiary IBD centre. The primary objective was to identify MRE findings 46 weeks after initiating biologic therapy that predict adverse long-term CD-related outcomes. Biologic therapies included infliximab/adalimumab in 70, vedolizumab in 5, and ustekinumab in 14. Presence of severe lesions (MaRIA ≥11) in any intestinal segment was associated with an increased risk of surgery (odds ratio [OR] 11.6), surgery or endoscopic balloon dilation (OR 6.3), and clinical relapse (OR 4.6). Penetrating lesions were associated with an increased risk of surgery (OR 3.4). In multivariable analysis, the only independent predictor of one or more adverse outcomes was the presence of strictures and/or penetrating complications. Creeping mesenteric fat was associated with an increased risk for hospitalisation (OR 5.1) and a need for corticosteroids (OR 16.0).⁷

The role of MRE in CD assessments continues to expand from a sensitive and specific diagnostic modality to a potential monitoring and prognostic instrument. This extremely important study⁷ is a foundation step towards the creation of a robust radiologic treatment target. Importantly, 90% of patients had persistent bowel wall abnormalities after 1 year of treatment, in keeping with earlier reports that this goal is achieved in a minority of patients.³ Like the response criteria set forth by Deepak et al.,¹ it suggests that more achievable targets short of transmural healing (i.e., absence of severe inflammation, strictures, and penetrating complications) will substantially reduce adverse long-term outcomes. Importantly, this study identified imaging criteria that can be obtained at a single time point after initiation of biologic therapy (46 weeks) to guide therapeutic decision making and risk assessment. Future research endeavours are likely to include a multi-site validation study utilising both MRE and IUS.

靶向治疗，特别是透壁放射治疗，是克罗恩病 (CD) 管理算法中的一个潜在关键概念。目前，通过内窥镜评估评估粘膜愈合情况是炎症性肠病（IBD）最常用的随访评估。¹然而，由于“节段跳跃”和/或壁内疾病，内窥镜技术对于整体肠道疾病询问可能不是最佳选择。²此外，对于透壁愈合或多模态放射学目标，目前还没有一个全球公认和有效的定义。³

各种 CD 成像测试已被评估为潜在的预后工具。磁共振小肠造影 (MRE) 和计算机断层扫描小肠造影可以识别药物治疗的放射学反应，这与降低住院、手术和/或皮质类固醇使用的长期风险有关。¹肠道超声 (IUS) 中回肠末端肠壁厚度的早期（8 周）减少（>18% 减少）可预测 CD 儿童的内镜缓解，为此目的，IUS 的表现优于症状和 C 反应蛋白。⁴然而，关于后续个体 MRE 成像参数和磁共振活动指数 (MaRIA) 评分的潜在预后意义的数据很少。^{5, 6}

费尔南德斯-克洛泰等人。试图通过对三级 IBD 中心的一项前瞻性纵向研究中的 89 名患者（58 名未接受过生物学治疗）进行事后分析来探讨这个问题。主要目标是确定开始生物治疗后 46 周的 MRE 结果，以预测与 CD 相关的长期不良结局。生物疗法包括 70 例患者使用英夫利昔单抗/阿达木单抗，5 例患者使用维多珠单抗，14 例患者使用乌特克单抗。任何肠道段存在严重病变 (MaRIA ≥11) 均与手术风险增加相关（比值比 [OR] 11.6）、手术或内镜球囊扩张（OR 6.3）和临床复发（OR 4.6）。穿透性病变与手术风险增加相关（OR 3.4）。在多变量分析中，一种或多种不良结果的唯一独立预测因素是狭窄和/或穿透性并发症的存在。肠系膜脂肪蠕动与住院风险增加（OR 5.1）和皮质类固醇需求增加（OR 16.0）相关。⁷

MRE 在 CD 评估中的作用不断从敏感且特异的诊断方式扩展到潜在的监测和预后工具。这项极其重要的研究⁷是朝着创建稳健的放射治疗目标迈出的基础一步。重要的是，90% 的患者在治疗 1 年后出现持续性肠壁异常，这与早期报告一致，即少数患者实现了这一目标。³与 Deepak 等人提出的反应标准一样，¹它表明，在没有透壁愈合的情况下，更可实现的目标（即不存在严重炎症、狭窄和穿透性并发症）将大大减少不良的长期结果。重要的是，这项研究确定了可以在生物治疗开始后（46周）的单个时间点获得的影像学标准，以指导治疗决策和风险评估。未来的研究工作可能包括利用 MRE 和 IUS 进行多站点验证研究。