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Table 1 Classification system for mrTRG

From: MRI response rate after short-course radiotherapy on rectal cancer in the elderly comorbid patient: results from a retrospective cohort study

DescriptionGrade
Complete regression (absence of tumour signal and barely visible treatment related scar)mrTRG 1
Good regression (predominant low signal intensity fibrosis with no obvious areas of intermediate signal intensity)mrTRG 2
Moderate regression (low signal intensity fibrosis predominates but there are obvious areas of intermediate signal intensity)mrTRG 3
Slight regression (little areas of low signal intensity fibrosis or mucin but mostly tumor)mrTRG 4
No regression (intermediate signal intensity, same appearances as original tumor)mrTRG 5
  1. mrTRG Magnetic resonance tumour regression grade