Anal cancer is a cancer which arises from the anus, the distal opening of the gastrointestinal tract. Symptoms may include bleeding from the anus or a lump near the anus. Other symptoms may include pain, itchiness, or discharge from the anus. A change in bowel movements may also occur. Risk factors include human papillomavirus (HPV), HIV/AIDS, receptive anal sex, smoking, and many sexual partners. Anal cancer is typically a squamous cell carcinoma. Other types include adenocarcinoma, small cell carcinoma, and melanoma. Diagnosis is suspected based on physical examination and confirmed by tissue biopsy.

Human papillomavirus: Examination of squamous cell carcinoma tumor tissues from patients in Denmark and Sweden showed a high proportion of anal cancers to be positive for the types of HPV that are also associated with high risk of cervical cancer. In another study done, high-risk types of HPV, notably HPV-16, were detected in 84 percent of anal cancer specimens examinedSexual activity: Due to increased risk of exposure to HPV, having multiple sex partners and receptive anal intercourse greatly increases the likelihood of developing anal cancer, for men and women.

Since many, if not most, anal cancers derive from HPV 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. In 2010, Gardasil was approved in the US 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.

Previously, anal cancer was treated with surgery, and in early-stage disease (i.e., localised cancer of the anus without metastasis to the inguinal lymph nodes), surgery is often curative. The difficulty with surgery has been the necessity of removing the internal and external anal sphincter, with concomitant fecal incontinence. For this reason, many patients with anal cancer have required permanent colostomies. Median survival rates for people with distant metastases ranges from 8 to 34 months. Surgical resection with a permanent colostomies was the standard treatment until the 1970s, yielding 5-year overall survival of approximately 50%. The best overall survival rates are seen after combined radiation therapy combined with chemotherapy (5-FU + Mitomycin) in people with T2N0 and T3N0 categories of disease (5-y overall survival: 82%). 

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 human papillomavirus (HPV).

Regards
Amalia
Managing Editor
Journal of Clinical Oncology and Cancer Research.