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Anal cancer

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Anal cancer
SpecialtyOncology Edit this on Wikidata

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.

Prevalence

The American Cancer Society estimates that in 2008 about 5,070 new cases of anal cancer will be diagnosed in the United States (about 3,000 in women and 2,000 in men).[1] It is typically found in adults, average age early 60s.[1]

In the US, an estimated 680 people died of anal cancer in 2008, [1]

Symptoms

Symptoms of anal cancer include bloating and change in bowel habits, a lump near the anus, rectal bleeding, itching or discharge.[2] Women may experience lower back pain due to pressure the tumor exerts on the vagina, and vaginal dryness.

Risk factors

  • 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 (90% of the tumors from women, 100% of the tumors from homosexual men, and 58% of tumors from heterosexual men).[3] In another study done, high-risk types of HPV, notably HPV-16, were detected in 84 percent of anal cancer specimens examined.[4]
  • Sexual activity: Having multiple sex partners or having anal sex, due to the increased risk of exposure to the HPV virus.[5] Homosexual and bisexual men are 17 times more likely to develop anal cancer than heterosexual men.[6]
  • Smoking: Current smokers are several times more likely to develop anal cancer compared with nonsmokers.[5]
  • Immunosuppression, which is often associated with HIV infection.[5]
  • Benign anal lesions (inflammatory bowel disease (IBD),[7] hemorrhoids, fistulae or cicatrices). Inflammation resulting from benign anal lesions, such as hemorrhoids and anal fistulas, has been considered to cause a predisposition to anal cancer. [8][9]

Prevention

Since many, if not most, anal cancers derive from human papillomavirus infections, and since the HPV vaccine prevents infection by some strains of the virus and has been shown to reduce the incidence of potentially precancerous lesions,[10] scientists surmise that HPV vaccination may reduce the incidence of anal cancer.[11]

Screening

Anal Pap smears similar to those used in cervical cancer screening have been studied for early detection of anal cancer in high-risk individuals.[12][13]

Treatment

Localised disease

Anal cancer is most effectively 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 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.

Metastatic or recurrent disease

Up to 10% of patients treated for anal cancer will develop distant metastatic disease. Metastatic or recurrent anal cancer is difficult to treat, and usually requires chemotherapy. Radiation is also employed to palliate specific locations of disease that may be causing symptoms. Chemotherapy commonly used is similar to other squamous cell epithelial neoplasms, such as platinum analogues, anthracyclines such as doxorubicin, and antimetabolites such as 5-FU and capecitabine. J.D. Hainsworth developed a protocol that includes Taxol and Carboplatinum along with 5-FU.

Prognosis

Based on series of 270 patients, the five year survival by stage was:[citation needed]

T1 – 86 percent
T2 – 86 percent
T3 – 60 percent
T4 – 45 percent
N0 – 76 percent
Node-positive – 54 percent

See also

References

  1. ^ a b c "Detailed Guide: Anal Cancer What Are the Key Statistics About Anal Cancer?". Retrieved 2008-11-18.
  2. ^ National Cancer Institute. Anal Cancer Treatment (PDQ®) Patient Version. 13 June 2008. Accessed 26 June 2009.
  3. ^ Danish Medical Bulletin. 2002 Aug;49(3):194-209
  4. ^ New England Journal of Medicine. 1997 Nov 6;337(19):1350-8
  5. ^ a b c American Cancer Society. "What Are the Risk Factors for Anal Cancer?"
  6. ^ "STD Facts - HPV and Men". Retrieved 2007-08-17.
  7. ^ M Frisch and C Johansen (2000). "Anal carcinoma in inflammatory bowel disease" (PDF). Anal carcinoma in inflammatory bowel disease. Retrieved 2008-01-22. {{cite web}}: Unknown parameter |publsiher= ignored (|publisher= suggested) (help); line feed character in |publsiher= at position 26 (help)
  8. ^ "Carcinoma of the Anus Management". 2007. Retrieved 2008-01-22. {{cite web}}: Text "Natia Esiashvili, Jerome Landry, Richard H. Matthews" ignored (help); Unknown parameter |publsiher= ignored (|publisher= suggested) (help)
  9. ^ "Benign Anal Lesions and the Risk of Anal Cancer". 1994. Retrieved 2008-01-22. {{cite web}}: Text "Morten Frisch, Jorgen H. Olsen, Andrea Bautz, and Mads Melbye" ignored (help); Unknown parameter |publsiher= ignored (|publisher= suggested) (help)
  10. ^ ""Gardasil, Merck's Cervical Cancer Vaccine, Demonstrated Efficacy in Preventing HPV-Related Disease in Males in Phase III Study: Pivotal Study Evaluating Efficacy of Gardasil in Males in Preventing HPV 6, 11, 16 and 18-Related External Genital Lesions"". Merck Research and Development News. (www.merck.com). Retrieved 2008-11-15.
  11. ^ Tuller, David (2007-01-31). "HPV vaccine may help to prevent anal cancer". International Herald Tribune. Retrieved 2009-al03-23. {{cite web}}: Check date values in: |accessdate= (help)
  12. ^ Cichoki, Mark. "Anal Papilloma Screening" on About.com
  13. ^ Chiao EY, Giordano TP, Palefsky JM, Tyring S, El Serag H (2006). "Screening HIV-infected individuals for anal cancer precursor lesions: a systematic review". Clin. Infect. Dis. 43 (2): 223–33. doi:10.1086/505219. PMID 16779751.{{cite journal}}: CS1 maint: multiple names: authors list (link)


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