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Anal cancer
Squamous cancer of the anal canal is usually linked to persistent HPV infection, and is treated with chemoradiation with 5-FU (or capecitabine) and mitomycin C — surgery is kept for residual or recurrent disease, to preserve the sphincter and the patient's quality of life and avoid a permanent stoma.
Why it matters in the exam
The typical exam stem shows a relatively young patient with severe pain and fresh bleeding on defecation and a hard mass on rectal examination, and asks about first treatment or the trial that showed the benefit of adding chemotherapy to radiation. It is important to distinguish it from rectal adenocarcinoma, whose treatment is completely different.
Another key point is the timing of response assessment: the tumour keeps shrinking for months after radiation ends, so an early biopsy can lead to unnecessary surgery. HIV, immunosuppression and smoking also appear as risk factors in the questions, so every new patient with anal cancer should be tested for HIV and have it controlled before treatment.
Key points
- Anal cancer is usually an HPV-related squamous carcinoma, and is more common in patients with HIV, immunosuppression or smoking.
- Chemoradiation with 5-FU or capecitabine and mitomycin C is first treatment, and it preserves the sphincter in most patients.
- Adding chemotherapy to radiation improved local control and colostomy-free survival, so radiation alone is kept for patients who cannot receive chemotherapy.
- Response assessment continues up to 26 weeks, because the tumour keeps shrinking; do not biopsy early without real suspicion.
- Abdominoperineal resection with a permanent stoma is kept for proven residual disease or local recurrence after chemoradiation.
Summary table
| Issue | What to know | Details |
|---|---|---|
| Risk factors | HPV (mainly type 16), HIV, immunosuppression, smoking | Usually squamous cell carcinoma |
| Work-up | Rectal examination, anoscopy and biopsy, pelvic MRI, PET-CT | Inguinal nodes are part of staging |
| Main treatment | Chemoradiation with 5-FU or capecitabine and mitomycin C | EORTC trial: adding chemotherapy to radiation improved local control and colostomy-free survival |
| Response assessment | Re-examination up to 26 weeks from start of treatment | Slow regression — do not biopsy early |
| Residual or local recurrence | Abdominoperineal resection (salvage surgery) | Permanent stoma |
| Metastatic disease | Carboplatin with paclitaxel, possibly with an added PD-1 inhibitor | A small well-differentiated anal margin lesion — local excision is possible |
| Treatment toxicity | Severe groin and perineal dermatitis, diarrhoea, and marrow suppression from mitomycin | IMRT reduces skin and bowel toxicity and allows the course to be completed without breaks |
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Sources
- NCCN Clinical Practice Guidelines in Oncology: Anal Carcinoma, 2026 — Principles of chemoradiation
- ESMO Clinical Practice Guideline: Anal cancer, 2021 — Diagnosis, treatment and follow-up
- Gunderson and Tepper's Clinical Radiation Oncology, 5th ed. (2021) — Anal carcinoma
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.