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| ==Overview== | | ==[[Anal cancer overview|Overview]]== |
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| '''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.
| | ==[[Anal cancer pathophysiology|Pathophysiology]]== |
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| ==Epidemiology== | | ==[[Anal cancer epidemiology and demographics|Epidemiology and Demographics]]== |
| '''Incidence'''<ref>Anal Carcinoma [http://www.thedoctorsdoctor.com/diseases/anal_ca.htm#epidemiology]</ref>
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| *In women and men who do not engage in anal intercourse with other men - 0.9/100,000
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| *In HIV negative men who engage in anal intercourse with other men - 35/100,000
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| *In HIV positive men who engage in anal intercourse with other men - (estimated) 60-70/100,000
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| Anal cancer is uncommon and accounts for only 4% of all cancers of the lower alimentary tract. There are estimated to be 4,650 new cases and 690 deaths from anal cancer in the United States in 2007.<ref>National Cancer Institute: Anal Cancer [http://www.nci.nih.gov/cancertopics/pdq/treatment/anal/healthprofessional]</ref> | | ==[[Anal cancer risk factors|Risk Factors]]== |
| Because it is rare and because it occurs in a body part that is rarely discussed, most people are unaware of its existence.
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| ==Risk factors== | | ==[[Anal cancer screening|Screening]]== |
| *[[Human papillomavirus]] (HPV) infection: An 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).<ref>Danish Medical Bulletin. 2002 Aug;49(3):194-209</ref> In another study done, high-risk types of HPV, notably HPV-16, were detected in 84 percent of anal cancer specimens examined.<ref>New England Journal of Medicine. 1997 Nov 6;337(19):1350-8</ref>
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| *Sexual activity: Having multiple sex partners or having [[anal sex]], due to the increased risk of exposure to the HPV virus.<ref name="ACS">American Cancer Society. [http://www.cancer.org/docroot/CRI/content/CRI_2_4_2X_What_are_the_risk_factors_for_Anal_Cancer_47.asp?sitearea "What Are the Risk Factors for Anal Cancer?"]</ref>
| | ==[[Anal cancer natural history|Natural History, Complications and Prognosis]]== |
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| *[[Smoking]]: Current smokers are several times more likely to develop anal cancer compared with nonsmokers.<ref name="ACS">American Cancer Society. [http://www.cancer.org/docroot/CRI/content/CRI_2_4_2X_What_are_the_risk_factors_for_Anal_Cancer_47.asp?sitearea "What Are the Risk Factors for Anal Cancer?"]</ref>
| | ==[[Anal cancer classification|Classification]]== |
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| *[[Immunosuppression]], which is often associated with [[HIV]] infection.<ref name="ACS">American Cancer Society. [http://www.cancer.org/docroot/CRI/content/CRI_2_4_2X_What_are_the_risk_factors_for_Anal_Cancer_47.asp?sitearea "What Are the Risk Factors for Anal Cancer?"]</ref>
| | ==[[Anal cancer causes|Causes]]== |
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| ==Prevention== | | ==[[Anal cancer differential diagnosis|Differentiating Anal cancer from other Disorders]]== |
| Since many, if not most, anal cancers derive from [[Human Papilloma Virus]] infections, and since the [[HPV vaccine]] prevents infection by several strains of the virus, scientists surmise that HPV vaccination will prevent anal cancer. <ref>{{http://www.iht.com/articles/2007/01/31/healthscience/sncancer.php}}</ref>
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| ==Screening== | | == Diagnosis == |
| Anal [[pap smear]]s similar to those used in [[cervical cancer]] screening have been studied experimentally for early detection of anal cancer in high-risk individuals.<ref>Cichoki, Mark. [http://aids.about.com/cs/conditions/a/analpaps.htm "Anal Papilloma Screening"] on About.com</ref><ref>{{cite journal |author=Chiao EY, Giordano TP, Palefsky JM, Tyring S, El Serag H |title=Screening HIV-infected individuals for anal cancer precursor lesions: a systematic review |journal=Clin. Infect. Dis. |volume=43 |issue=2 |pages=223-33 |year=2006 |pmid=16779751 |doi=10.1086/505219}}</ref> | | |
| | :[[Anal cancer history and symptoms| History and Symptoms]] | [[Anal cancer physical examination | Physical Examination]] | [[Anal cancer staging | Staging]] | [[Anal cancer laboratory studies | Lab Studies]] | [[Anal cancer electrocardiogram|Electrocardiogram]] | [[Anal cancer chest x ray|Chest X Ray]] | [[Anal cancer MRI|MRI]] | [[Anal cancer CT|CT]] | [[Anal cancer echocardiography|Echocardiography]] | [[Anal cancer other imaging findings|Other imaging findings]] |
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| ==Treatment== | | ==Treatment== |
| ===Localized disease===
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| Anal cancer is most effectively treated with surgery, and in early stage disease (i.e., localized 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]].
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| 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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| ===Metastatic or recurrent disease===
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| 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]].
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| ==Prognosis==
| | :'''Medical:''' [[Anal cancer medical therapy| Medical Therapy]] |
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| | :'''Surgical:''' [[Anal cancer surgery| Surgery]] |
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| | ==[[Anal cancer prognosis|Prognosis]]== |
| | ==Case Studies== |
| == See also == | | == See also == |
| *[[Anal wart]]s | | *[[Anal wart]]s |