Doctors Revision

Oncology

Colorectal & Anal Cancer

Malignant tumours arising from the lining of the colon, rectum (colorectal cancer - CRC, predominantly adenocarcinoma) or anus (anal cancer - predominantly squamous cell carcinoma, often related to HPV).

Also known as: Colon Cancer, Rectal Cancer, Bowel Cancer, Anal Cancer

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Referral and warning signs

When to refer

Referral for Colonoscopy/Sigmoidoscopy if: Rectal bleeding (unless clear source like fissure/haemorrhoids in young patient). Change in bowel habit >40-50yrs. Iron deficiency anaemia (unexplained). Positive FOBT/FIT. Alarm features. Refer confirmed cases to specialized cancer centre.

Red flags

  • Rectal bleeding (especially if mixed with stool or dark blood)
  • Persistent change in bowel habit
  • Unexplained iron deficiency anaemia
  • Palpable abdominal or rectal mass
  • Unintentional weight loss
  • Symptoms of bowel obstruction

Signs and symptoms

  • Change in bowel habits (persistent diarrhoea, constipation, or change in stool calibre/consistency).
  • Rectal bleeding (bright red or dark blood mixed with stool).
  • Abdominal pain, cramps, or discomfort.
  • Sensation of incomplete bowel emptying (tenesmus).
  • Iron deficiency anaemia (due to chronic occult bleeding, esp. right-sided colon cancer).
  • Unexplained weight loss.
  • Fatigue.
  • Palpable abdominal mass (late stage).
  • Symptoms of bowel obstruction (if tumour blocking lumen).
  • Anal Cancer specific: Anal pain, itching, bleeding, lump near anus, change in bowel control.

Risk factors

  • Colorectal Cancer (CRC): Age (>50 years), Personal history of colorectal polyps (especially adenomas) or CRC, Inflammatory Bowel Disease (Ulcerative Colitis, Crohn's Disease), Family history of CRC or polyps (esp. 1st degree relative, early onset), Inherited genetic syndromes (Lynch syndrome/HNPCC, Familial Adenomatous Polyposis - FAP), Diet high in red/processed meat, low in fibre, Obesity, physical inactivity, Smoking, heavy alcohol use, Diabetes Mellitus.
  • Anal Cancer: Human Papillomavirus (HPV) infection (especially types 16, 18), HIV infection / Immunosuppression, History of receptive anal intercourse, Smoking, History of cervical/vulvar cancer or pre-cancer.

Diagnosis

Clinical assessment

Suspect CRC in patients with change in bowel habit, rectal bleeding, iron deficiency anaemia, or other persistent GI symptoms, especially if >45-50 years or risk factors present. Suspect anal cancer with anal pain/bleeding/mass. Digital Rectal Exam (DRE) essential.

Investigations

  • Colonoscopy: Gold standard for CRC diagnosis and screening. Allows visualization of entire colon/rectum, biopsy of suspicious lesions, removal of polyps.
  • Flexible Sigmoidoscopy: Visualizes rectum and sigmoid colon only.
  • Faecal Occult Blood Test (FOBT) / Faecal Immunochemical Test (FIT): Screening tests for occult blood; positive result requires colonoscopy.
  • CT Colonography ('Virtual Colonoscopy'): Alternative imaging screening/diagnostic test.
  • Barium Enema (Double contrast): Less used now, may show filling defects.
  • Anal Cancer Diagnosis: Inspection, DRE, Anoscopy with Biopsy of suspicious lesion.
  • Staging Investigations (CRC): CT scan (Chest, Abdomen, Pelvis) +/- MRI (for rectal cancer staging) +/- PET-CT.
  • Blood tests: CBC (anaemia), LFTs (liver mets), CEA (Carcinoembryonic Antigen - tumour marker for monitoring, not screening).
  • HPV testing/typing (relevant for anal cancer).

Diagnostic criteria

Histopathological confirmation from biopsy obtained via colonoscopy/anoscopy.

Management

Non-pharmacological management

  • Referral to specialized multidisciplinary team (Colorectal Surgery, Oncology, Radiation Oncology) at Cancer Centre.
  • Management depends on type (colon vs rectal vs anal) and stage.
  • Colorectal Cancer: Surgery (Resection of tumour with adequate margins and regional lymph nodes) is mainstay of curative treatment (Colectomy, Anterior Resection, Abdominoperineal Resection). Adjuvant Chemotherapy (Stage III/high-risk Stage II colon). Neoadjuvant/Adjuvant Chemoradiotherapy (Locally advanced Rectal). Palliative chemotherapy +/- targeted therapy/immunotherapy for metastatic disease.
  • Anal Cancer: Chemoradiotherapy is primary treatment for most stages. Surgery reserved for residual/recurrent disease.

Pharmacological treatment

  • Chemotherapy regimens (CRC): FOLFOX, FOLFIRI, CapeOx, +/- targeted agents (Bevacizumab, Cetuximab/Panitumumab - based on RAS/BRAF mutation status).
  • Chemoradiotherapy regimens (Rectal/Anal): Often 5-Fluorouracil (5-FU) + Mitomycin C or Capecitabine based, concurrent with radiation.
  • Pain management, antiemetics, supportive care.

Monitoring

Monitor treatment response/toxicity. Surveillance after curative treatment (CEA, Colonoscopy, CT scans) to detect recurrence.

Complications

  • Bowel obstruction
  • Perforation
  • Bleeding / Anaemia
  • Fistula formation
  • Metastatic disease (liver, lung, peritoneum)
  • Complications of surgery (anastomotic leak, infection, stoma issues)
  • Complications of chemo/radiotherapy

Prevention

  • CRC Screening: Colonoscopy, FIT/FOBT, Sigmoidoscopy starting age 45-50 (or earlier if high risk). Polyp removal prevents progression to cancer.
  • Lifestyle: Healthy diet (high fibre, low red/processed meat), maintain healthy weight, physical activity, limit alcohol, smoking cessation.
  • Aspirin (low dose) may reduce risk (discuss with doctor).
  • HPV vaccination (may reduce anal cancer risk).

Patient education

  • Explain diagnosis, type (colon/rectal/anal), and stage.
  • Discuss treatment options and goals (curative/palliative).
  • Explain surgery, chemotherapy, radiotherapy procedures and side effects.
  • Importance of screening for prevention/early detection.
  • Lifestyle factors.
  • Stoma care education if applicable.
  • Importance of follow-up and surveillance.

Uganda-specific notes

CRC incidence rising. Anal cancer associated with HPV/HIV. Late presentation common. Access to screening (colonoscopy), pathology, staging, surgery, chemo/radiotherapy limited.

References

  • Uganda Clinical Guidelines (UCG) 2023

    Chapter 12, Section 12.3.2

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