When surgery would significantly impair anal sphincter functions, radiotherapy is an effective alternative, usually with chemotherapy .
External radiation therapy for small lesions—with or without chemotherapy—may also be used to avoid surgery and/or avoid a colostomy . Surgery may be necessary for large lesions that do not shrink with radiotherapy and chemotherapy.
Combination chemotherapy with 5-fluorouracil (5-FU) + mitomycin-C with primary radiation therapy is more effective for larger lesions than radiation therapy alone in reducing the need for surgery and/or a colostomy. Cisplatin + 5-FU is an alternative treatment with radiotherapy. Both combinations seem to be equally effective.
The former standard approach—an abdominal-perineal resection (APR), which involves removal of the anus and rectum and requires a colostomy—is now rarely used except for recurrent disease. If there is still tumor in the anal canal after non-surgical treatment, the surgery that will be required ranges from a local sphincter preservation operation to a complete abdominal-perineal resection with colostomy.
