Colorectal Cancer

Visualise tumour, obtain tissue for histology and molecular testing. Gold standard for diagnosis.

Local T and N staging of rectal tumours — complements MRI for early (T1-T2) disease.

Full staging — assess liver, lung, lymph node, and peritoneal involvement.

Essential for rectal cancer — assesses mesorectal fascia, T-stage, lymph nodes, and surgical resectability. Guides neoadjuvant treatment decisions.

Characterise liver metastases — distinguishes resectable from unresectable disease.

Detect occult metastases before planned liver resection or in rising CEA with negative CT.

Baseline tumour marker. Elevated in ~70% of CRC. Used for monitoring response and detecting recurrence.

Baseline organ function, anaemia assessment, liver involvement.

Determines eligibility for anti-EGFR therapy (cetuximab, panitumumab). Mutation in any codon excludes anti-EGFR benefit.

Identifies BRAF V600E mutant subgroup — poor prognosis, specific targeted therapy (encorafenib + cetuximab).

MSI-H/dMMR determines immunotherapy eligibility. Stage II MSI-H predicts against 5-FU benefit. Lynch syndrome screening.

HER2 amplification identifies targetable alteration (~2–3%). Test in RAS/BRAF WT metastatic CRC.

MLH1, MSH2, MSH6, PMS2 germline mutations. Identifies Lynch syndrome — implications for patient and family screening.

Primary resection of colon tumour. Curative intent for non-metastatic disease. Right hemicolectomy for right-sided; left hemicolectomy or sigmoidectomy for left/sigmoid tumours.

Rectal cancer — sphincter-preserving surgery for upper/mid rectum. Often preceded by neoadjuvant chemoradiation to downstage.

Very low rectal cancer where sphincter cannot be preserved. Results in permanent colostomy.

Resection of oligometastatic liver or lung disease — potentially curative in selected Stage IV patients.

Peritoneal metastases — cytoreductive surgery plus heated intraperitoneal chemotherapy in selected centres.

Stage III adjuvant (6 months post-resection). Metastatic first-line backbone. Most common CRC chemotherapy regimen.

Oral alternative to FOLFOX — same efficacy, convenient 3-weekly cycle. Stage III adjuvant or metastatic first-line.

Metastatic second-line (after FOLFOX failure) or first-line with bevacizumab.

Aggressive triplet regimen for young, fit patients with high-volume metastatic disease. Often combined with bevacizumab.

Oral fluoropyrimidine — used as monotherapy in elderly/frail, or combined with oxaliplatin (CAPOX).

Locally advanced rectal cancer (T3-4, N+) — long-course CRT (45–50 Gy + capecitabine) or short-course RT (5×5 Gy) to downstage before surgery.

Stereotactic ablative radiotherapy for liver or lung oligometastases — alternative to surgery when resection not feasible.

Anti-VEGF antibody added to FOLFOX, FOLFIRI, or FOLFOXIRI. First-line metastatic. Particularly important in KRAS-mutant tumours where anti-EGFR is not an option.

Anti-EGFR — only in RAS/BRAF wild-type, left-sided tumours. Combined with FOLFOX or FOLFIRI first-line. Improves response rate and OS.

Fully human anti-EGFR antibody — same indications as cetuximab. Less infusion reaction risk. Combined with FOLFOX first-line or monotherapy later lines.

BRAF V600E-mutant metastatic CRC — second-line standard of care after KEYNOTE-177 or first-line chemotherapy. Significantly improved OS over chemotherapy.

KRAS G12C-specific inhibitor. Small subset of CRC (~3–4%) with KRAS G12C mutation. FDA-approved second-line.

HER2-amplified metastatic CRC — FDA-approved regimen for previously treated HER2+ CRC.

MSI-H / dMMR metastatic CRC — FDA-approved first-line (KEYNOTE-177). Dramatically improves PFS and OS vs chemotherapy. Also used for refractory MSI-H CRC.

MSI-H / dMMR metastatic CRC — second-line after pembrolizumab or first-line alternative. Nivolumab monotherapy or dual checkpoint (CheckMate-142).