Prospective evaluation of MR-TRG (Tumor Regression Grade) in esophageal cancer after neo-adjuvant therapy: Preliminary results

Purpose: To develop MRI-based criteria to assess tumor response to neoadjuvant therapies (NAT) of esophageal cancers (EC) and to evaluate its diagnostic performance in predicting the pathological Tumor Regression Grade (pTRG). Method: From 2018 to 2022, patients with newly diagnosed locally advanced EC underwent MRI examinations for initial staging and restaging after NAT. Magnetic Resonance TRG (MR-TRG), equivalent to the Mandard and Becker classifications, were developed and independently assessed by two radiologists, blinded to pTRG, using T2W and DW-MR Images. All patients underwent surgery and benefited from a blinded pTRG evaluation by two pathologists. The agreement between readers and between MR-TRG and pTRG were assessed with Cohen's Kappa. The correlation of MR-TRG and pTRG was determined using Spearman's correlation. Results: 28 patients were included. Interrater agreement was substantial between radiologists, improved when grouping grade 1 and 2 (kappa = 0.78 rose to 0,84 for Mandard and 0.68 to 0,78 for Becker score). Agreement between pTRG and MR-TRG was moderate with a percentaged agreement (p) = 87.5 %, kappa (kappa) = 0.54 and p = 83.3 %, kappa = 0.49 for Mandard and Becker, respectively. Agreement was improved to substantial when grouping grades 1-2 for Mandard and 1a-1b for Becker with p = 89.3 %, kappa = 0.65 and p = 85.2 %, kappa = 0.65 respectively. Sensitivity and specificity of MR-TRG in predicting pTRG were 88.2 % and 72.7 % for Mandard system (scores 1-2 versus 3-5), and 83.3 % and 80 % for Becker system (scores 1a-1b versus 2-3). Conclusion: A substantial agreement between MR-TRG and pTRG was achieved when grouping grade 1-2. Hence, MR-TRG could be used as a surrogate of complete and near-complete pTRG.