Surgery for anal cancer
Historically, all but the smallest anal cancers were treated with a radical surgery called abdominoperineal or AP 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 without radical surgery 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 for anal cancer
Radiation therapy alone for localized anal cancer may confer a greater than a 70% likelihood of 5-year survival. The high doses (high-energy) 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 radiation treatment approach is not favored today. However, intensity-modulated radiation therapy where the radiation is shaped to treat only the cancer area is the most common type of radiation treatment for anal cancer. In addition, proton therapy is being tested and may provide even better outcomes for some patients.
Combination chemotherapy and radiation therapy for anal cancer
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 the 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 follow-up of 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.
What are treatment options for stage IV anal cancer or metastasis?
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 surgery
- Palliative radiation therapy
- Palliative combined chemotherapy and radiation
- Clinical trials
Is it possible to prevent anal cancer?
Preventive steps of demonstrable benefit include:
- Receive HPV vaccination
- Avoidance of high risk behaviors which increase the risk of or facilitate the acquisition of HPV infection such as having multiple sexual partners and engaging in receptive anal intercourse
- Perform anal pap testing in patients with a past history of carcinomas of the cervix (cervical cancer), vagina, or vulva (These increase the risk of anal cancer three-fold. Detection and treatment of precancerous lesions can reduce the risk that these patients will require treatment for anal cancer in the future.)
- Stop smoking, since smoking increases the risk of anal cancer
- Avoid high risk behaviors for the acquisition of HIV disease (Chronic immunosuppression in men who have sex with men increases the risk of anal cancer 30-fold.)
- Carefully monitor transplant recipients on immunosuppressant drugs with anal pap smears as discussed (Transplant recipients have a three-fold increased risk of anal cancer.)
Where can one find information about clinical trials or research for anal cancer?
There is ongoing research in the treatment of anal cancer. Visit ClinicalTrials.gov for information on clinical trials and patient eligibility.
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Edge, S.B., et al. "Anal Cancer." AJCC Cancer Staging Manual, 7th Ed. New York, NY: Springer, 2010.
"NCCN Clinical Practice Guidelines in Oncology: Anal Carcinoma." Version 1.2017.
"PDQ National Cancer Institute Summaries: Anal Cancer." 2017.