PassFinals
Colorectal Surgery

Colorectal Cancer

Colorectal cancer is usually an adenocarcinoma of the colon or rectum whose presentation, local treatment and chance of cure depend on site, TNM stage and tumour biology; FIT helps select symptomatic patients for referral but cannot safely rule cancer out when clinical concern persists.

In a nutshell

Colorectal cancer may be detected by screening or present with rectal bleeding, altered bowel habit, iron-deficiency anaemia, weight loss, pain or a mass. Symptomatic FIT at or above the NICE threshold triggers suspected-cancer referral, but a lower or unreturned FIT never overrides a mass, persistent symptoms, anaemia or strong clinical concern. Colon and rectal cancers require site-specific MDT treatment, and selected metastatic disease remains potentially curable.

Classic presentation

An older adult has persistent change in bowel habit with blood mixed into stool, or otherwise unexplained iron-deficiency anaemia and weight loss, followed by colonoscopic biopsy showing adenocarcinoma.

Key points

  • Offer symptomatic FIT to the NG12 symptom and age groups; refer at 10 µg Hb/g faeces or above, but safety-net and refer below threshold when concern persists.
  • A rectal mass or unexplained anal mass or ulceration does not need FIT before suspected-cancer referral is considered.
  • Population screening is separate from symptomatic FIT: England, Scotland and Wales invite ages 50 to 74 every 2 years, Northern Ireland invites ages 60 to 74, and England and Scotland allow opt-in from age 75.
  • The symptomatic pathway may select colonoscopy or CT colonography as the first whole-colon test according to clinical and patient factors; only colonoscopy supplies biopsy and polypectomy.
  • Stage with CT chest, abdomen and pelvis, add dedicated pelvic MRI for rectal cancer, and use the current UICC TNM system. Dukes staging is historical only.
  • Test every new colorectal cancer for MMR deficiency or MSI; test RAS and BRAF V600E when metastatic disease may receive systemic anticancer treatment.
  • Stage III colon cancer usually receives adjuvant systemic therapy, while higher-risk M0 rectal cancer commonly receives preoperative radiotherapy or chemoradiotherapy before surgery (see BNF).
  • Liver, lung or peritoneal metastases require specialist resectability review; metastatic disease is not synonymous with non-curative treatment.
  • Confirmed Lynch syndrome needs colonoscopy every 2 years from age 25 for MLH1, MSH2 or EPCAM and from age 35 for MSH6 or PMS2, usually to age 75.

First-line investigation

Use quantitative FIT first in the eligible symptomatic primary-care pathway, unless a rectal or anal lesion or strong clinical concern warrants referral without waiting; definitive diagnosis requires colonic imaging and tissue, usually colonoscopy with biopsy.

Management

Recognise emergency colorectal cancer

  • Obstruction requires ABCDE, nil by mouth, intravenous resuscitation, bloods including lactate, urgent contrast CT when safe and immediate senior colorectal and anaesthetic review. For acute left-sided malignant obstruction, specialist options are palliative stenting or, when cure is possible, a choice of stent or emergency surgery.2,6
  • Peritonism or sepsis suggests perforation: start the sepsis and intra-abdominal infection pathway, give local empirical antimicrobials and obtain urgent surgical source control; do not delay intervention in instability (see BNF).8,2,6
  • Major rectal bleeding needs resuscitation and the acute lower-GI bleeding pathway. Continued instability or suspected active bleeding after resuscitation requires CT angiography, followed promptly by embolisation when appropriate.9

Refer, diagnose and stage

  • Offer symptomatic FIT to the precise NG12 groups and refer at 10 µg Hb/g faeces or above. A lower or unreturned result requires active safety-netting and must not delay referral for a mass, anaemia, persistent symptoms or strong concern.4,7
  • Do not confuse screening with symptomatic triage or apply the symptomatic FIT threshold to screening results. England, Scotland and Wales invite ages 50 to 74 every 2 years; Northern Ireland invites ages 60 to 74. England and Scotland allow people aged 75 or over to request a kit.3,13,14,15,4
  • Clinical triage may select colonoscopy or CT colonography as the first whole-colon test; colonoscopy provides tissue, while a CTC-only lesion needs a separate tissue route. Stage with CT chest, abdomen and pelvis, add pelvic MRI for rectal cancer and use current UICC TNM9, not historical Dukes staging.2,5,12

Treat colon and rectal cancer differently

  • Resect localised colon cancer en bloc with the regional lymphovascular drainage; laparoscopic or open surgery is selected for oncological and operative safety, and cT4 disease may merit preoperative systemic treatment (see BNF).2,16
  • For cT1 to cT2, cN0, M0 rectal cancer, discuss local excision or endoscopic options against total mesorectal excision and functional consequences. Do not give preoperative radiotherapy for early rectal cancer outside a trial, and keep transanal total mesorectal excision within formal research.2,17
  • For M0 rectal cancer that is cT1 to cT2 with cN1 to cN2, or cT3 to cT4 with any N stage, offer preoperative radiotherapy or chemoradiotherapy and then operable disease resection. A complete response managed without surgery needs informed consent and intensive specialist surveillance (see BNF).2,16
  • Specialist contact X-ray brachytherapy may be considered only when a rectal tumour is 3 cm or smaller, no more advanced than T3b N1 M0, and surgery is declined or unacceptably risky; metastatic use is research-only.18

Use pathology, genomics and metastatic resectability

  • For stage III colon cancer, offer 3 months of CAPOX. If unsuitable, offer FOLFOX with individualised duration, or a single fluoropyrimidine when combination treatment is unsuitable. Apply these NICE options to stage III rectal cancer after short-course preoperative radiotherapy or no preoperative treatment, not automatically after long-course treatment (see BNF).2,16
  • Test every new tumour for MMR or MSI and complete the sequential Lynch pathway. In metastatic disease also test RAS and BRAF V600E, then match systemic classes to performance status, goals, prior treatment and biology under current NICE technology appraisals (see BNF).1,2,16
  • Refer potentially limited liver, lung or peritoneal metastases to the relevant specialist MDT for resection or local-treatment assessment before labelling disease incurable.2
  • Confirmed Lynch syndrome requires colonoscopy every 2 years, starting at age 25 for MLH1, MSH2 or EPCAM and age 35 for MSH6 or PMS2, usually to age 75 and then according to fitness and retained bowel. This is not FIT screening.19,20

Surveillance, stoma care and late effects

  • After potentially curative surgery for non-metastatic disease, measure CEA at least every 6 months and obtain at least 2 CT chest, abdomen and pelvis scans in the first 3 years; perform clearance colonoscopy within 1 year of diagnosis and, when appropriate, repeat after 3 further years.2,22,11
  • Discuss temporary or permanent stoma risk before treatment and involve a trained stoma professional. Offer a three-stage enhanced recovery programme for elective major or complex surgery, and screen for bowel, urinary and sexual dysfunction, low anterior resection syndrome, neuropathy, nutrition, psychological distress and return-to-work needs.2,21
  • New bleeding, altered bowel habit, weight loss, abdominal pain, a mass, obstruction symptoms or systemic deterioration requires prompt reassessment rather than waiting for the next surveillance appointment.4,2

Exam traps

  • A FIT below 10 µg Hb/g faeces does not exclude colorectal cancer; persistent symptoms, anaemia, a mass or strong clinical concern still require safety-netting and appropriate referral.
  • Do not require FIT before considering referral for a rectal mass or unexplained anal mass or ulceration.
  • Do not use a previous negative screening FIT to dismiss new symptoms; symptomatic and screening FIT pathways serve different populations.
  • CT colonography can show a cancer but cannot provide histology; tissue is still required where feasible.
  • CEA is for baseline and surveillance support, not primary diagnosis or exclusion.
  • Dukes staging may appear in older trials and examination stems, but current UK MDT and pathology practice uses UICC TNM9.
  • Proximal anaemia and distal obstruction are useful tendencies, not anatomical rules.
  • MMR or MSI testing is universal at diagnosis for Lynch assessment; RAS and BRAF V600E testing is specifically required when metastatic disease may receive systemic therapy.
  • Metastatic colorectal cancer is not automatically incurable: limited liver, lung or peritoneal disease may be amenable to specialist resection or local treatment.
  • Do not substitute population FIT screening for confirmed-Lynch surveillance; pathogenic variant carriers need gene-specific-start, 2-yearly colonoscopy.
  • A clinical complete response after rectal neoadjuvant treatment is not routine discharge from surgery; organ-preserving surveillance is intensive and specialist-led.
  • Transanal total mesorectal excision remains research-only, whereas contact X-ray brachytherapy has a narrow specialist option defined by tumour size, stage and surgical preference or risk.

Illustrations

Major pathways from precursor lesion to colorectal cancerDiagram showing conventional adenoma and serrated precursor routes, with chromosomal instability and mismatch-repair-deficient or microsatellite-unstable pathways rather than a compulsory single mutation sequence.PassFinals · original
Typical proximal and distal colorectal cancer presentationsColon schematic contrasting the tendency for proximal tumours to cause occult blood loss and iron deficiency with the tendency for distal or rectal tumours to cause visible bleeding, altered bowel habit and obstruction, while emphasising that patterns overlap.PassFinals · original
Resected colon with carcinoma and nearby polypsGross surgical specimen showing a colorectal carcinoma with adjacent polyps, illustrating that synchronous precursor lesions may coexist with an established cancer.Bernstein0275, Wikimedia Commons · CC-BY-SA-3.0

Key sources

  1. NICE, Molecular testing strategies for Lynch syndrome in people with colorectal cancer (HTG430)Published 22 Feb 2017
  2. NICE, Colorectal cancer: diagnosis and management (NG151)Published 29 Jan 2020 | Updated 15 Dec 2021
  3. NHS England, Bowel cancer screening programme overviewPublished 1 Jan 2015 | Updated 17 Mar 2026
  4. NICE, Suspected cancer: recognition and referral (NG12)Published 23 Jun 2015 | Updated 15 Apr 2026
  5. NHS England, Implementing a timed colorectal cancer diagnostic pathway, version 3.2 (PR2119)
  6. ACPGBI, Consensus guidelines in emergency colorectal surgeryPublished 27 Feb 2021
  7. NICE, Quantitative faecal immunochemical testing to guide colorectal cancer pathway referral in primary care (HTG690)Published 24 Aug 2023
  8. NICE, Suspected sepsis in people aged 16 or over: recognition, assessment and early management (NG253)Published 19 Nov 2025
  9. British Society of Gastroenterology, Diagnosis and management of acute lower gastrointestinal bleeding
  10. NHS England, National Genomic Test DirectoriesPublished 3 Aug 2018 | Updated 16 Jul 2026
  11. BSG/ACPGBI/PHE, Post-polypectomy and post-colorectal cancer resection surveillance guidelinePublished 27 Nov 2019
  12. Royal College of Pathologists, UICC TNM9 classification of colorectal tumours
  13. NHS inform, Bowel screening in Scotland
  14. Public Health Wales, Bowel screening
  15. nidirect, Bowel cancer screening
  16. BNF, Cytotoxic drugs treatment summary
  17. NICE, Transanal total mesorectal excision for rectal cancer (HTG603)Published 15 Dec 2021
  18. NICE, Low-energy contact X-ray brachytherapy for rectal cancer (HTG763)Published 13 Nov 2025
  19. BSG/ACPGBI/UKCGG, Guidelines for the management of hereditary colorectal cancerPublished 28 Nov 2019
  20. NHS England, Lynch syndrome colonoscopy surveillance care pathwayUpdated 6 Mar 2026
  21. NICE, Perioperative care in adults (NG180)Published 19 Aug 2020
  22. NICE, Colorectal cancer quality standard (QS20)Published 13 Aug 2012 | Updated 1 Feb 2022

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.