Korean J Radiol.  2020 Sep;21(9):1065-1076. 10.3348/kjr.2019.0797.

Prognostic Value of Tumor Regression Grade on MR in Rectal Cancer: A Large-Scale, Single-Center Experience

• Yoen H
• Park HE
• Kim SH
• Yoon JH
• Hur BY
• Bae JS
• Kim JH
• Oh HJ
• Han JK

• KMID: 2505747
• DOI: http://doi.org/10.3348/kjr.2019.0797

Abstract

Objective
To determine the prognostic value of MRI-based tumor regression grading (mrTRG) in rectal cancer compared withpathological tumor regression grading (pTRG), and to assess the effect of diffusion-weighted imaging (DWI) on interobserveragreement for evaluating mrTRG.
Materials and Methods
Between 2007 and 2016, we retrospectively enrolled 321 patients (male:female = 208:113; meanage, 60.2 years) with rectal cancer who underwent both pre-chemoradiotherapy (CRT) and post-CRT MRI. Two radiologistsindependently determined mrTRG using a 5-point grading system with and without DWI in a one-month interval. Two pathologistsgraded pTRG using a 5-point grading system in consensus. Kaplan-Meier estimation and Cox-proportional hazard models wereused for survival analysis. Cohen’s kappa analysis was used to determine interobserver agreement.
Results
According to mrTRG on MRI with DWI, there were 6 mrTRG 1, 48 mrTRG 2, 109 mrTRG 3, 152 mrTRG 4, and 6 mrTRG 5.By pTRG, there were 7 pTRG 1, 59 pTRG 2, 180 pTRG 3, 73 pTRG 4, and 2 pTRG 5. A 5-year overall survival (OS) was significantlydifferent according to the 5-point grading mrTRG (p= 0.024) and pTRG (p= 0.038). The 5-year disease-free survival (DFS)was significantly different among the five mrTRG groups (p= 0.039), but not among the five pTRG groups (p= 0.072). OSand DFS were significantly different according to post-CRT MR variables: extramural venous invasion after CRT (hazard ratio= 2.259 for OS, hazard ratio = 5.011 for DFS) and extramesorectal lymph node (hazard ratio = 2.610 for DFS). For mrTRG, kvalue between the two radiologists was 0.309 (fair agreement) without DWI and slightly improved to 0.376 with DWI.
Conclusion
mrTRG may predict OS and DFS comparably or even better compared to pTRG. The addition of DWI on T2-weightedMRI may improve interobserver agreement on mrTRG.

Keyword

Rectal neoplasm; Regression; Magnetic resonance imaging; Prognosis; Survival analysis