Colorectal cancer

Quick Overview

Colorectal cancer (CRC) is the 4th most common UK cancer. Early detection via two-week wait (2WW) referrals and structured MDT-led management improves survival. NICE NG151 emphasizes complete TME resection, neoadjuvant therapy for locally advanced rectal cancer, and CEA-based surveillance to detect recurrence early.

Core Facts & Concepts

Two-Week Wait Referral Criteria (NICE NG151)

• Age ≥40: Unexplained weight loss + abdominal pain
• Age ≥50: Unexplained rectal bleeding
• Age ≥60: Iron-deficiency anaemia OR change in bowel habit
• Any age: Positive FIT (≥10 µg Hb/g faeces) OR rectal/abdominal mass OR rectal examination findings suspicious for cancer

TNM Staging Essentials

• T1: Submucosa invasion | T2: Muscularis propria | T3: Subserosa/pericolic fat | T4: Adjacent organs/peritoneum
• N1: 1-3 nodes | N2: ≥4 nodes
• M1a: Single distant site | M1b: Multiple sites


Critical Measurements

• CRM (circumferential resection margin): Must be >1mm for R0 resection
• Distal margin: ≥2cm for rectal cancer (≥1cm acceptable with neoadjuvant therapy)
• Baseline CEA: Measure pre-operatively for surveillance comparison

Problem-Solving Approach

MDT Decision-Making for Rectal Cancer

1. MRI pelvis: Assess tumour height (from anal verge), T-stage, nodal status, extramural vascular invasion (EMVI), CRM involvement
2. Neoadjuvant therapy indications:
   • Short-course radiotherapy (5Gy × 5): T3a-b, N0, no EMVI, CRM clear
   • Long-course chemoradiotherapy (45-50Gy + capecitabine): T3c-d/T4, N+, EMVI+, threatened CRM (<1mm)
3. Surgery timing: 6-12 weeks post-radiotherapy
4. TME principles: Sharp dissection in mesorectal plane, en-bloc excision, intact mesorectal fascia


Post-Operative Surveillance (NICE NG151)

• CEA: Every 3 months (Years 1-2), every 6 months (Year 3)
  • Threshold: Rising CEA prompts CT chest/abdomen/pelvis
• CT CAP: 6 months, 12 months, 3 years (high-risk Stage III)
• Colonoscopy: 1 year post-op, then 3-yearly if normal

Analysis Framework

Red Flags for Local Recurrence 🚩 Incomplete TME (coning, mesorectal defects >5mm) 🚩 Positive CRM (<1mm) 🚩 EMVI positivity 🚩 Poor response to neoadjuvant therapy (mrTRG 4-5)

Visual Aid

Key Points Summary

✓ 2WW triggers: Age ≥40 + weight loss + abdominal pain; ≥50 + rectal bleeding; ≥60 + IDA/bowel habit change; positive FIT ≥10 µg/g

✓ Rectal MRI mandatory: Determines neoadjuvant therapy (T3c+, N+, EMVI+, CRM <1mm = long-course chemoRT)

✓ TME gold standard: Sharp mesorectal dissection, CRM >1mm required for R0 resection

✓ CEA surveillance: Every 3 months (Years 1-2), every 6 months (Year 3); rising CEA → CT CAP

✓ Adjuvant chemotherapy: All Stage III colon cancer; consider Stage II if high-risk (T4, perforation, <12 nodes, poor differentiation)

✓ Neoadjuvant timing: Surgery 6-12 weeks post-radiotherapy for optimal tumour regression

⭐ Clinical Pearl: A threatened CRM on MRI (<1mm) is the single strongest predictor of local recurrence-always mandates neoadjuvant therapy before TME surgery.