Anal cancer treatment involves a variety of therapies including surgery, radiation, chemotherapy, or a combination of these.
Historically, all but the smallest anal cancers were treated with a radical surgery called abdominoperineal resection leading to a permanent end colostomy. About 70% of patients survived more than 5 years in limited studies of this approach. This is no longer the primary anal cancer treatment of choice. Chemotherapy and radiation are now favored.
A limited resection of small stage I cancers can be curative for these small cancers of the anal margin or perianal skin when the anal sphincter is not involved. Radical resection today is reserved for some cases of residual or recurrent cancer in the anal canal after non-operative treatment. Other nonsurgical approaches (involving chemotherapy with a radiation boost or radioactive seed applications) may be used to avoid colostomy in those circumstances.
Radiation therapy alone for localized anal cancer may confer a greater than a 70% likelihood of 5 year survival. The high doses of radiation used (over 60 Gy [Gy is a unit of energy absorbed from ionizing radiation or 1 joule/Kg of matter]) can lead to significant tissue damage and scarring sometimes necessitating colostomy surgery for control and repair. This approach is not favored today.
Combination chemotherapy and radiation therapy
Today the optimal primary therapy for stage I, II, IIIA, and IIIB anal cancers that are too large for potentially curative local resection is the combination of lower doses of radiation therapy (45 to 60 Gy) combined with two older chemotherapy medicines, 5-FU and Mitomycin C. The combination treatment results in 5-year colostomy free survival of over 75% of stage I, 65% of stage II, and 40% to 50% of stage 3 anal cancer cases. Anal cancers that are located in an area where they cannot be resected may benefit from combination therapy.
Salvage chemotherapy with an alternative regimen of the medicines 5-FU and cisplatin combined with a radiation boost can be used for residual or recurrent local disease to avoid radical surgery. Radioactive seed implants can be used to establish local control for residual or recurrent disease to avoid radical surgery.
Stage IV anal cancer or metastasis treatment
Today there is no standard chemotherapy with curative potential for metastatic disease. Local symptom control, referred to as palliative care, is extremely important.
Rare patients with stage IV disease have truly localized metastatic disease for which surgery to remove the metastasis could theoretically be curative. This option should be considered in those unusual cases. The disease is rare enough that there are no studies specifically supporting or refuting this approach.
Patients with stage IV disease are excellent candidates for clinical research trials if they are well enough and give truly informed consent. A clinical trial is a research study investigating new approaches to treatment which may benefit the patient and help develop treatments for those patients who develop this disease in the future.
Thus for most patients with stage IV disease the treatment options include:
Palliative radiation therapy
Palliative combined chemotherapy and radiation