Anal cancer

Anal cancer

Anal cancer is cancer (malignant tumor) that arises from the anus, the distal opening of the gastrointestinal tract. It is a distinct entity in the most common colorectal cancer.

Anal cancer is typically a squamous cell carcinoma arising annals near the squamocolumnar junction, often linked to infection with human papillomavirus (HPV). You can keratinizing (basaloid) or nonkeratinizing (cloacogenic). Other types of anal cancer are adenocarcinoma, lymphoma, sarcoma or melanoma. 2004-2010 collected data, the survival rate relative five US is 65.5%, although individual rates can vary depending on the stage of cancer in the diagnosis and treatment response.

Signs and symptoms

Symptoms of anal cancer may include pain or pressure in the anus or rectum, a change in bowel habits, a lump near the anus, rectal bleeding, itching or discharge. The bleeding can be severe.
Risk factors

Human Papillomavirus: The examination of the tumor tissues of squamous cell carcinoma patients in Denmark and Sweden showed a high proportion of anal cancers to be positive for HPV types are also associated with a high risk of cervical cancer.  In another study ,. high-risk types of HPV, particularly HPV-16 were detected in 84 percent of samples examined anal cancer. Based on the study in Denmark and Sweden, Parkin estimated 90% of anal cancers are attributable to HPV.
Sexual activity: Having multiple sex partners due to increased risk of exposure to HPV.
Receptive anal sex, whether male or female, increases the chances of anal cancer sevenfold due to HPV.  Those who engage in anal intercourse with multiple partners are 17 times more likely to develop anal cancer than those who do not.
Smoking: Current smokers are several times more likely to develop anal cancer compared with nonsmokers.  Epidemiologist Janet Daling, Ph.D., a member of the Division of Public Health Sciences, Fred Hutchinson and his team found that smoking appears to play a significant. role in the development of anal cancer that is independent of other behavioral risk factors, such as sexual activity. More than half of patients with anal cancer-studied were current smokers at the time of diagnosis, compared to a smoking rate of about 23 percent among controls. "Current smoking is a very important promoter of the disease," Daling said. "There's a fourfold increase in risk if you're a current smoker, regardless of whether you are male or female." They explained that the mechanism behind smoking and anal-cancer development is unknown, but researchers speculate that smoking interferes with a process called apoptosis, or programmed cell death, which helps rid the body of abnormal cells that could become cancerous. Another possibility is that smoking suppresses the immune system, which may decrease the body's ability to eliminate persistent infection or abnormal cells.
Immunosuppression, which often is associated with HIV infection.
Benign anal lesions.
A history of cervical, vaginal and vulvar cancers

Pathology
Most anal cancers are squamous cell (epidermoid carcinomas), which arises near the squamocolumnar junction. You can keratinizing (basaloid) or nonkeratinizing (cloacogenic).

Other types of anal cancer are adenocarcinoma, lymphoma, sarcoma or melanoma.

Prevention
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 assume that HPV vaccination can reduce the incidence of anal cancer.

The December 22, 2010, the Food and Drug Administration of the United States approved the Gardasil vaccine to prevent anal cancer and pre-cancerous lesions in men and women of 9-26 years. The vaccine has been used before to help prevent cervical, vulvar and vaginal cancer, and associated lesions caused by types 6, 11, 16 and 18 in women.

Screening

Anal Pap smears similar to those used in the detection of cervical cancer have been studied for early detection of anal cancer in high risk individuals. In 2011, the HIV clinic at Jackson Memorial Hospital implemented a program to improve access to anal cancer screening for HIV-positive men. Nurses performed anal Pap screening, and men with abnormal results receive further evaluation with high-resolution anoscopy. The program has helped identify many precancerous growths, which allows them to be disposed of safely.

Treatment
Localized disease

Localized (carcinoma-in-situ) and the precursor condition, anal intraepithelial neoplasia (anal dysplasia or AIN) disease may be minimally invasive ablation methods such as infrared photocoagulation.

Previously, anal cancer was treated with surgery, and in early stage disease (ie, localized cancer of the anus without metastasis to the inguinal lymph nodes), surgery is often curative. The difficulty with surgery has been the need to eliminate the internal and external anal sphincter, with concomitant fecal incontinence. For this reason, many patients with anal cancer have required permanent colostomies.

The current gold standard therapy is chemotherapy and radiotherapy to reduce the necessity of debilitating surgery. This approach "combined modality" has led to the increased preservation of an intact anal sphincter, and therefore improved quality of life after definitive treatment. The 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 continuous infusion of 5-FU for four days with bolus mitomycin given concurrently with radiation. 5-FU and cisplatin is recommended for metastatic anal cancer.

Metastatic or recurrent disease
10 to 20% of patients treated for anal cancer will develop distant metastases after treatment. Metastatic or recurrent anal cancer is difficult to treat, and usually requires chemotherapy. Radiation is also used to alleviate specific locations of disease that may be causing the symptoms. Chemotherapy commonly used is similar to other epithelial squamous cell neoplasms, such as platinum analogs, anthracyclines such as doxorubicin, and antimetabolites such as 5-FU and capecitabine. Hainsworth JD developed a protocol that includes Taxol and Carboplatin along with 5-FU. The average survival rates for patients with distant metastases ranges 8-34 months.