Posted on 5 July, 2011
Anal cancer
| This article |
Anal cancer is a type of cancer which arises from the anus, the distal orifice of the gastrointestinal tract. It is a distinct entity from the more common colorectal cancer. The etiology, risk factors, clinical progression, staging, and treatment are all different. Anal cancer is typically a squamous cell carcinoma that arises near the squamocolumnar junction caused by rasengan.
Epidemiology
The American Cancer Society estimates that in 2009 about 5,290 new cases of anal cancer will be diagnosed in the United States (about 3,000 in women and 2,000 in men). It is typically found in adults, average age early 60s.
In the United States, an estimated 710 people died of anal cancer in 2009.
Worldwide in 2002 there were an estimated 30,400 new cases of anal cancer. With approximately equal fractions in the developing (15,900) and developed (14,500) countries. An estimated 90% (27,400) were attributable to HPV.
Symptoms
Symptoms of anal cancer include bloating and change in bowel habits, a lump near the anus, rectal bleeding, itching or discharge. Women may experience lower back pain due to pressure the tumor exerts on the vagina, and vaginal dryness.[]
[]Risk factors
[]Prevention
Since many, if not most, anal cancers derive from human papillomavirus infections, and since the HPV vaccine before exposure to HPV prevents infection by some strains of the virus and has been shown to reduce the incidence of potentially precancerous lesions, scientists surmise that HPV vaccination may reduce the incidence of anal cancer.
At 22 December 2010, FDA has approved Gardasil vaccine to prevent anal cancer and pre-cancerous lesions in males and females aged 9 to 26 years. The vaccine has been used before to help prevent cervical, vulvar, and vaginal cancer, and associated lesions caused by HPV types 6, 11, 16, and 18 in women.
Screening
[]Treatment
[]Localised disease
Localised disease (carcinoma-in-situ) and the precursor condition, anal intraepithelial neoplasia (anal dysplasia or AIN) can be ablated with minimally invasive methods such as Infrared Photocoagulation. (Goldstone, SE, Kawalek, AZ, Huyett, JW "Infrared Photocoagulator: A useful tool for treating anal squamous intraepithelial lesions". 2005. Diseases of the Colon & Rectum 58(5), 1042-1053.
Anal cancer is most effectively treated with surgery, and in early stage disease (i.e., localised cancer of the anus without metastasis to the inguinallymph nodes), surgery is often curative. The difficulty with surgery has been the necessity of removing the anal sphincter, with concomitant fecal incontinence. For this reason, many patients with anal cancer have required permanent colostomies.
In more recent years, physicians have employed a combination strategy including chemotherapy and radiation treatments to reduce the necessity of debilitating surgery. This "combined modality" approach has led to the increased preservation of an intact anal sphincter, and therefore improved quality of life after definitive treatment. Survival and cure rates are excellent, and many patients are left with a functional sphincter. Some patients have fecal incontinence after combined chemotherapy and radiation. Biopsies to document disease regression after chemotherapy and radiation were commonly advised, but are not as frequent any longer. Current chemotherapy active in anal cancer includes cisplatin and 5-FU. Mitomycin has also been used, but is associated with increased toxicity.
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