Anal cancer (also called Squamous Cell Carcinoma of the Anus or SCCA) is a skin cancer that arises from inside the anal canal or from the skin around the anus (anal verge). There are other rare types of anal cancer.
Approximately 1 in 600 men and women will get anal cancer in their lifetime. Almost 6000 new cases are diagnosed each year in the US.
Risk factors for anal cancer include immunodeficiency (eg HIV, transplant patients), those who have had previous Anal Warts due to the Human Papilloma Virus (HPV) serotypes 16 & 18, and those with Anal Intraepithelial Neoplasia (AIN). The estimated life time risk of anal cancer in HIV-ve men who have sex with men (HIV –ve MSM) is 30 times that of the average population. The lifetime risk of anal cancer in HIV-positive men who have sex with men (HIV +ve MSM) is 100 times that of the average population.
Anal cancer may be felt as a lump on digital rectal examination (DRE), or may not be noticeable at all. It may bleed from time to time. Patients might have recurring pain in the anal area. Discharge from the anus. Changes in the bowel habits.
Screening of high risk populations such as men who have sex with men (MSM) and those with anal warts due to HPV infection is recommended. Screening methods most commonly used include the Pap smear and anoscopy after painting the area with vinegar (acetic acid). These tests will allow for identification of those with anal dysplasia (AIN) which is a known risk factor for anal cancer. High risk populations (e.g HIV +ve MSM) and those with high grade AIN should have annual digital rectal examination (DRE).
- Any suspicious lesion or lump in the anal region should be examined and biopsied. Four quadrant biopsies inside and outside of the perianal region are required in the high risk HIV+ve MSM patients where AIN status needs to be determined.
- Office examination includes examination of the groin lymph nodes.
- CT scan of chest, abdomen and pelvis, MRI pelvis/ Endorectal ultrasound (ERUS), PET CT scan for nodes.
- HIV testing is done for high risk.
COURSE AND PROGNOSIS
Anal cancer is locally aggressive, but distant spread (metastases) less common than many other cancers. It responds well to chemoradiotherapy. Overall survival is 70% at 5 years, but is dependent on the stage at which it is picked up.
Very small anal cancers can be managed with surgical excision alone provided this surgery does not involve damage to the anal sphincter. However, for larger lesions, the management is primary chemoradiotherapy and not surgery.
Your surgeon is important in making the diagnosis and the ongoing surveillance of anal cancer following chemoradiotherapy treatment. Occasionally biopsies are required after radiotherapy treatment to confirm that treatment has been successful. This should not occur before 12 weeks have passed since finishing therapy. Occasionally salvage surgery is required after failed response to radiotherapy. This can range from local excision with skin grafting to more radical surgery including removal of the anus and rectum (abdominoperineal resection) with the creation of a permanent stoma.
Anal cancer responds well to radiotherapy combined with a small dose of chemotherapy (mitomycin C or cisplatin), with surgery as primary treatment only used for Superficially Invasive Squamous Cell Carcinoma of the Anus (SISCCA), or for larger cancers where primary chemoradiotherapy has failed.
Sometimes during the course of chemoradiation therapy, patient might need a temporary diverting colostomy based on their tolerance for chemoradiation treatment.
Routine examination with digital rectal exam and anoscopy every 3months in the first 2 years, and every 6 months until 5 years.
Persistent/residual (<6months) or recurrent (>6 months) disease localized to the pelvis after chemoradiation- salvage APR therapy. Study with MRI pelvis, PET CT to differentiate tumor from scar.
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