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 ACS 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 will die of anal cancer in 2008.[1]
Risk factors
* 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).[2] In another study done, high-risk types of HPV, notably HPV-16, were detected in 84 percent of anal cancer specimens examined.[3]
* Sexual activity: Having multiple sex partners or having anal sex, due to the increased risk of exposure to the HPV virus.[4]
* Smoking: Current smokers are several times more likely to develop anal cancer compared with nonsmokers.[4]
* Immunosuppression, which is often associated with HIV infection.[4]
* Benign anal lesions. (inflammatory bowel disease (IBD)[5], 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 [6] [7]
* Men who have sex with men are 17 times more likely to develop anal cancer than men who do not have sex with men.[8]
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 some potentirally precancerous lesions[9], scientists surmise that HPV vaccination may prevent anal cancer.[10]
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.[11][12] There is concern among researchers that the CDC is exhibiting prejudice and homophobia toward their stance on anal papsmear and cancer prevention. According to the CDC’s fact sheet, "there is no clear benefit to knowing you have this virus – since HPV in unlikely to affect your health and cannot be treated." But some researchers believes that HPV can and does affect the health of thousands of men, especially those living with HIV. In a 1987 report, it was estimated that incidence of anal cancer among HIV-negative men who engage in receptive anal intercourse with other men was up to 35/100,000 – a rate on a par with the incidence of cervical cancer before routine Pap smears were initiated in the 1940s. The incidence of anal cancer among gay men with AIDS was suggested in one report to be twice that of men of the same age, race, and sexual orientation in the years before AIDS (1975 to 1979). In other words, the incidence of anal cancer may be more than 70 of every 100,000 HIV-infected men who have a history of receptive anal intercourse with other men. In one San Francisco cohort consisting of more than 600 MSM, anal dysplasia was found in 36% of the HIV-positive men and 7% of the HIV-negative men. According to Dr. Joel Palefsky of the University of California, San Francisco, these and other observations "would suggest that we should be mounting all-out campaigns to educate people around these issues and immediately implement screening and treatment programs to prevent anal cancer, modeled after the highly successful programs to prevent cervical cancer."[13]
Treatment
Localized disease
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.
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
Prevalence
The ACS 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 will die of anal cancer in 2008.[1]
Risk factors
* 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).[2] In another study done, high-risk types of HPV, notably HPV-16, were detected in 84 percent of anal cancer specimens examined.[3]
* Sexual activity: Having multiple sex partners or having anal sex, due to the increased risk of exposure to the HPV virus.[4]
* Smoking: Current smokers are several times more likely to develop anal cancer compared with nonsmokers.[4]
* Immunosuppression, which is often associated with HIV infection.[4]
* Benign anal lesions. (inflammatory bowel disease (IBD)[5], 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 [6] [7]
* Men who have sex with men are 17 times more likely to develop anal cancer than men who do not have sex with men.[8]
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 some potentirally precancerous lesions[9], scientists surmise that HPV vaccination may prevent anal cancer.[10]
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.[11][12] There is concern among researchers that the CDC is exhibiting prejudice and homophobia toward their stance on anal papsmear and cancer prevention. According to the CDC’s fact sheet, "there is no clear benefit to knowing you have this virus – since HPV in unlikely to affect your health and cannot be treated." But some researchers believes that HPV can and does affect the health of thousands of men, especially those living with HIV. In a 1987 report, it was estimated that incidence of anal cancer among HIV-negative men who engage in receptive anal intercourse with other men was up to 35/100,000 – a rate on a par with the incidence of cervical cancer before routine Pap smears were initiated in the 1940s. The incidence of anal cancer among gay men with AIDS was suggested in one report to be twice that of men of the same age, race, and sexual orientation in the years before AIDS (1975 to 1979). In other words, the incidence of anal cancer may be more than 70 of every 100,000 HIV-infected men who have a history of receptive anal intercourse with other men. In one San Francisco cohort consisting of more than 600 MSM, anal dysplasia was found in 36% of the HIV-positive men and 7% of the HIV-negative men. According to Dr. Joel Palefsky of the University of California, San Francisco, these and other observations "would suggest that we should be mounting all-out campaigns to educate people around these issues and immediately implement screening and treatment programs to prevent anal cancer, modeled after the highly successful programs to prevent cervical cancer."[13]
Treatment
Localized disease
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.
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
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