A patient with T3N1M0 (Stage IIIB) mid-rectal adenocarcinoma undergoes long-course chemoradiation (45–50 Gy + 5-FU) followed by total mesorectal excision. Pathology shows ypT0N0 (complete pathological response). According to current evidence and 'Watch-and-Wait' protocols, which assessment tool is used to determine eligibility for non-operative management of near-complete clinical response?
- A Memorial Sloan Kettering Cancer Center (MSKCC) prognostic nomogram
- B Mandard Tumor Regression Grade (TRG 1–5)
- C MRI-based mrTRG (magnetic resonance tumor regression grade) ✓
- D CEA level < 5 ng/mL post-treatment
Correct answer: C. MRI-based mrTRG (magnetic resonance tumor regression grade)
Explanation
The mrTRG (MRI-based Tumor Regression Grade) system assesses fibrosis versus residual tumor signal intensity on post-treatment MRI and is the key imaging tool used in 'Watch-and-Wait' protocols (Habr-Gama, MERCURY II) to identify near-complete clinical response candidates for non-operative management. mrTRG 1–2 (predominantly fibrosis) suggests excellent response. Mandard TRG is a histopathological classification applied to resected specimens, not a tool for predicting or selecting non-operative management.
Reference: Bailey & Love's Short Practice of Surgery, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.