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Colorectal cancer
Most colorectal cancers develop from an adenomatous polyp over years, so screening can prevent them; colon cancer is treated with resection including lymph nodes and adjuvant chemotherapy in stage III, and in locally advanced rectal cancer treatment before surgery is given according to pelvic MRI.
Why it matters in the exam
The exam asks about colorectal cancer from three directions. The first is screening: from when, with which test and how often — for average-risk people, for those with an affected first-degree relative, and for carriers of Lynch syndrome or FAP. The second is presentation: a right-sided tumour usually presents with iron-deficiency anaemia and fatigue, and a left-sided tumour with a change in bowel habit, blood in the stool and obstruction. Iron-deficiency anaemia in a man or a post-menopausal woman requires gastrointestinal investigation, and Streptococcus gallolyticus bacteraemia requires colonoscopy.
The third direction is treatment by stage: work-up (complete colonoscopy, CT of the chest, abdomen and pelvis, CEA, and for the rectum a pelvic MRI), resection with at least 12 lymph nodes, adjuvant chemotherapy in stage III, and for the rectum — treatment before surgery for locally advanced tumours and total mesorectal excision (TME). Candidates are also asked about resectable liver metastases, an obstructing left-sided tumour, and follow-up with CEA and colonoscopy after surgery.
Key points
- Average-risk screening: FIT every year at age 50–74; a positive result — colonoscopy.
- First-degree relative before age 60 — colonoscopy from age 40 every 5 years; Lynch — every 1–2 years from age 20–25.
- Right — anaemia; left — change in bowel habit and obstruction.
- Colon: resection with at least 12 nodes; adjuvant chemotherapy in stage III.
- Locally advanced rectum: MRI, treatment before surgery and TME.
Summary table
| Situation | Finding or group | Recommendation |
|---|---|---|
| Average-risk screening | Age 50–74 (in the USA from 45) | Faecal immunochemical test (FIT) every year, or colonoscopy every 10 years; a positive result — colonoscopy |
| First-degree relative with cancer before age 60 | Increased risk | Colonoscopy from age 40, or 10 years earlier than the age at which the relative was diagnosed, every 5 years |
| Lynch syndrome | MLH1, MSH2, MSH6, PMS2 | Colonoscopy every 1–2 years from age 20–25; also consider gynaecological prevention |
| Colon cancer stages I–III | No distant metastases | Resection with at least 12 lymph nodes; adjuvant chemotherapy in stage III and in high-risk stage II |
| Locally advanced rectal cancer | T3–T4 or positive nodes on MRI | Treatment before surgery (chemoradiation or total neoadjuvant therapy), then TME |
| Liver metastases | Resectable | Chemotherapy and resection of the metastases — cure is possible |
In the full version for subscribers
- A simple algorithm
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Sources
- NCCN Clinical Practice Guidelines in Oncology: Colon Cancer and Rectal Cancer, 2025 — Work-up, surgery and adjuvant or neoadjuvant therapy
- ESMO Clinical Practice Guidelines: localised colon cancer; localised rectal cancer, 2020 and 2017 (updated) — Staging and multimodal treatment
- Israel Ministry of Health, national programme for early detection of colorectal cancer, current — Faecal occult blood screening age 50–74
- Sabiston Textbook of Surgery, 21st edition (2022) — Colon and Rectum
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-02. The text may contain errors; when in doubt, check the source.