Ep 142 – Colorectal cancer

Colorectal cancer (CRC) is the fourth most common malignancy in the UK and a major cause of morbidity and mortality. It refers to malignancies that arise from the caecum to the rectum and can be detected on screening, on imaging or endoscopy, or following presentation with change in bowel habit, iron deficiency anaemia or bowel obstruction. Its management depends on the stage of the disease and patient factors, with treatment options including surgical resection, chemotherapy and radiotherapy. In this episode, Dr Roger Henderson gives an overview of CRC and looks at how to achieve early diagnosis, which is essential for effective treatment and the greatest chance of survival.

Key take-home points

• Bowel or colorectal cancer (CRC) is the third most common cancer worldwide and the second highest cause of cancer death.
• In the UK, CRC is the fourth most common cancer after breast, prostate and lung cancer, and it accounts for around 11% of all new cancer cases with around 44,000 cases each year.
• Proximal colon tumours are more common in women and older patients, whereas distal lesions are more common in men and younger patients.
• Rates of bowel cancer appear to be increasing in the under-50 age group.
• After age, family history is the most common risk factor.
• Family cancer syndromes, such as familial adenomatous polyposis and Lynch syndrome, are associated with 2% to 5% of all colon cancers.
• Obesity increases the risk of developing CRC as well as being associated with a greater risk of dying from the disease.
• The most common presenting symptoms and signs of cancer or large polyps are rectal bleeding, persisting change in bowel habit and anaemia. The presentation depends on the site of the cancer.
• Between 6% and 10% of patients with iron-deficiency anaemia will be found to have CRC, most commonly on the right side of the colon.
• The NICE changed its guidance in 2023 and advises that faecal immunochemical testing is used to guide referral for suspected CRC.
• Complete examination of the colon is indicated in patients with suspected CRC.
• Carcinoembryonic antigen (CEA) testing is not sufficiently sensitive or specific to be used for diagnosis in symptomatic patients, or as a screening tool in the asymptomatic population.
• Magnetic resonance imaging is more specific than computed tomography in showing liver metastases.
• NICE guidance states that testing for Lynch syndrome should now be offered to all people with CRC when first diagnosed.
• CRC is staged using the tumour, node and metastases (TNM) classification. More information on staging can be found in reference 10.
• Surgery remains the definitive treatment for apparently localised CRC. Both radiotherapy and chemotherapy can improve survival rates after potentially curative surgery.
• Around half of people diagnosed with CRC survive for at least 5 years after diagnosis.
• The 5-year survival rate is 90.9% for people with localised cancer, 73.4% for cancer that has spread to regional lymph nodes and 15.6% for distant metastases at diagnosis.

Key references

1. Duan B, et al. In: Gastrointestinal Cancers [Internet]. Brisbane (AU): Exon Publications; 2022 Sep 30. Chapter 1. doi: 10.36255/exon-publications-gastrointestinal-cancers-colorectal-cancer.
2. Cancer Research UK. https://www.cancerresearchuk.org/health-professional/cancer-statistics/statistics-by-cancer-type/bowel-cancer#heading-Two.
3. Dong Y, et al. Biosci Rep. 2017;37(6):BSR20170945. doi: 10.1042/BSR20170945.
4. Menon G, et al. StatPearls [Internet]. 2024. https://www.ncbi.nlm.nih.gov/books/NBK470380/.
5. NICE. 2021. https://www.nice.org.uk/guidance/ng151/.
6. NICE. 2023. https://www.nice.org.uk/guidance/ng12.
7. NICE. 2023. https://www.nice.org.uk/guidance/dg56.
8. Cancer Research UK. https://www.cancerresearchuk.org/about-cancer/bowel-cancer.
9. Sung H, et al. Lancet Oncol. 2024:S1470-2045(24)00600-4. doi: 10.1016/S1470-2045(24)00600-4.
10. Cancer Research UK. https://www.cancerresearchuk.org/about-cancer/bowel-cancer/stages-types-and-grades.