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Lower GI: Rectal MRI risk stratification and neoadjuvant selection

Free question published 08 October 2026

Lower GIRectal MRI risk stratification and neoadjuvant selection

A 64-year-old man has a mid-rectal adenocarcinoma 8 cm from the anal verge. Staging MRI reports a cT3b tumour extending 2 mm beyond the muscularis propria, no extramural venous invasion, two indeterminate 4 mm mesorectal nodes, and the closest tumour margin lies 6 mm from the mesorectal fascia. CT shows no metastases. The colorectal MDT debates whether to give preoperative radiotherapy. What is the most appropriate management?

  1. AShort-course preoperative radiotherapy (25 Gy in 5 fractions) followed by total mesorectal excision
  2. BTotal mesorectal excision without preoperative radiotherapy, as this is a tumour with good prognostic features on MRI
  3. CLong-course chemoradiotherapy followed by total mesorectal excision
  4. DTotal neoadjuvant therapy with consolidation chemotherapy
  5. EDefinitive chemoradiotherapy with a watch-and-wait strategy

Why B is correct

ESMO bases the neoadjuvant decision on MRI-defined risk of local recurrence rather than T stage alone, weighing the predicted circumferential resection margin (CRM), EMVI and the more advanced T3 substages (T3c/T3d). This tumour has favourable MRI features throughout: only 2 mm of extramural spread (T3b), no EMVI and a widely clear mesorectal fascia (6 mm). Where there is no MRI indication that surgery will yield an R1 or R2 resection, standard TME should achieve a curative resection and neoadjuvant downstaging is not necessary. Upfront TME without radiotherapy is therefore appropriate, sparing radiotherapy toxicity. The shallow extramural depth and clear margin are the decisive favourable MRI features.

And why the others are not

  • AIncorrect. Short-course radiotherapy adds toxicity without a clear benefit when the mesorectal fascia is widely clear and prognostic features are favourable.
  • CIncorrect. Long-course chemoradiotherapy is reserved for higher-risk tumours with a threatened margin, deeper extramural spread, EMVI or bulky nodal disease; it overtreats this good-prognosis lesion.
  • DIncorrect. Total neoadjuvant therapy is for high-risk locally advanced disease, not a good-prognosis early cT3b tumour.
  • EIncorrect. Definitive chemoradiotherapy with watch-and-wait is an organ-preservation strategy for selected patients seeking to avoid surgery, not the default for a resectable good-prognosis tumour.

Source ESMO Consensus Guidelines — management of rectal cancer (MRI risk stratification) — Glynne-Jones R, Wyrwicz L, Tiret E, et al. Rectal cancer: ESMO Clinical Practice Guidelines / ESMO Consensus Guidelines for management of patients with colon and rectal cancer. Ann Oncol.

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