Anal Cancer

Anal Cancer – Treatment Overview

Introduction
Anal cancer is a rare malignancy that arises from the tissues of the anal canal. The majority are squamous cell carcinomas (SCC), strongly associated with human papillomavirus (HPV), especially HPV-16. Risk factors include chronic HPV infection, HIV/AIDS, receptive anal intercourse, smoking, and immunosuppression. Symptoms may include rectal bleeding, anal pain, itching, or a mass.

Unlike many other cancers, anal cancer is usually treated with organ-preserving chemoradiotherapy rather than surgery, which allows patients to avoid permanent colostomy in most cases.

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Treatment Options

1. Localized Anal Squamous Cell Carcinoma

• Concurrent chemoradiotherapy (standard of care):

  • 5-Fluorouracil (5-FU): 1,000 mg/m²/day continuous IV infusion on days 1–4 and 29–32.

  • Mitomycin C: 10–12 mg/m² IV bolus on days 1 and 29.

  • Radiotherapy: 45–59 Gy over 5–6 weeks.

• Alternative: Capecitabine (oral prodrug of 5-FU) can replace 5-FU.

2. Small, Well-Differentiated Lesions (<2 cm, T1N0)

• Local excision with negative margins may be sufficient.

• Chemoradiotherapy still preferred if margins are uncertain or histology is unfavorable.

3. Locally Advanced / Persistent or Recurrent Disease

• Abdominoperineal resection (APR): Surgery with permanent colostomy, reserved for refractory or recurrent tumors after chemoradiotherapy.

• Re-irradiation or salvage chemotherapy may also be considered.

4. Metastatic Anal Cancer

• Systemic chemotherapy:

  • Carboplatin + Paclitaxel (preferred first-line).

  • Cisplatin + 5-FU is another option.

• Immunotherapy (for refractory disease):

  • Nivolumab 240 mg IV every 2 weeks or Pembrolizumab 200 mg IV every 3 weeks (especially in PD-L1+ or MSI-high disease).

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Supportive and Palliative Care

• Pain control with analgesics.

• Management of radiation proctitis and dermatitis.

• Nutritional support to prevent weight loss and malnutrition.

• Psychological support given stigma and quality-of-life issues.

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Prognosis

• 5-year survival:

  • Localized disease: ~70–80%.

  • Locally advanced: ~50–60%.

  • Metastatic: <20%.

• Prognosis is better with early detection and HPV-positive tumors.