Anal cancer
Encyclopedia
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. It may be keratinizing (basaloid) or non-keratinizing (cloacogenic). Other types of anal carcinoma are adenocarcinoma
, lymphoma
, sarcoma
or melanoma
.
estimates that in 2009 about 5,290 new cases of anal cancer will be diagnosed in the United States (about 3,000 in women and 2,000 in men). It is typically found in adults, average age early 60s.
In the United States, an estimated 710 people died of anal cancer in 2009.
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 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.
At 22 December 2010, FDA has approved Gardasil vaccine 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.
s similar to those used in cervical cancer
screening have been studied for early detection of anal cancer in high-risk individuals.
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.
. 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.
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
which arises from the anus
Anus
The anus is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, unwanted semi-solid matter produced during digestion, which, depending on the type of animal, may be one or more of: matter which the animal cannot digest,...
, the distal orifice of the gastrointestinal tract
Gastrointestinal tract
The human gastrointestinal tract refers to the stomach and intestine, and sometimes to all the structures from the mouth to the anus. ....
. It is a distinct entity from the more common colorectal cancer
Colorectal cancer
Colorectal cancer, commonly known as bowel cancer, is a cancer caused by uncontrolled cell growth , in the colon, rectum, or vermiform appendix. Colorectal cancer is clinically distinct from anal cancer, which affects the anus....
. The etiology
Etiology
Etiology is the study of causation, or origination. The word is derived from the Greek , aitiologia, "giving a reason for" ....
, risk factors, clinical progression, staging, and treatment are all different. Anal cancer is typically a squamous cell carcinoma
Squamous cell carcinoma
Squamous cell carcinoma , occasionally rendered as "squamous-cell carcinoma", is a histologically distinct form of cancer. It arises from the uncontrolled multiplication of malignant cells deriving from epithelium, or showing particular cytological or tissue architectural characteristics of...
that arises near the squamocolumnar junction. It may be keratinizing (basaloid) or non-keratinizing (cloacogenic). Other types of anal carcinoma are adenocarcinoma
Adenocarcinoma
Adenocarcinoma is a cancer of an epithelium that originates in glandular tissue. Epithelial tissue includes, but is not limited to, the surface layer of skin, glands and a variety of other tissue that lines the cavities and organs of the body. Epithelium can be derived embryologically from...
, lymphoma
Lymphoma
Lymphoma is a cancer in the lymphatic cells of the immune system. Typically, lymphomas present as a solid tumor of lymphoid cells. Treatment might involve chemotherapy and in some cases radiotherapy and/or bone marrow transplantation, and can be curable depending on the histology, type, and stage...
, sarcoma
Sarcoma
A sarcoma is a cancer that arises from transformed cells in one of a number of tissues that develop from embryonic mesoderm. Thus, sarcomas include tumors of bone, cartilage, fat, muscle, vascular, and hematopoietic tissues...
or melanoma
Melanoma
Melanoma is a malignant tumor of melanocytes. Melanocytes are cells that produce the dark pigment, melanin, which is responsible for the color of skin. They predominantly occur in skin, but are also found in other parts of the body, including the bowel and the eye...
.
Epidemiology
The American Cancer SocietyAmerican Cancer Society
The American Cancer Society is the "nationwide community-based voluntary health organization" dedicated, in their own words, "to eliminating cancer as a major health problem by preventing cancer, saving lives, and diminishing suffering from cancer, through research, education, advocacy, and...
estimates that in 2009 about 5,290 new cases of anal cancer will be diagnosed in the United States (about 3,000 in women and 2,000 in men). It is typically found in adults, average age early 60s.
In the United States, an estimated 710 people died of anal cancer in 2009.
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 HPV.
Symptoms
Symptoms of anal cancer include bloating and change in bowel habits, a lump near the anus, rectal bleeding, itching or discharge. Women may experience lower back pain due to pressure the tumor exerts on the vagina, and vaginal dryness.Risk factors
- Human papillomavirusHuman papillomavirusHuman papillomavirus is a member of the papillomavirus family of viruses that is capable of infecting humans. Like all papillomaviruses, HPVs establish productive infections only in keratinocytes of the skin or mucous membranes...
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 examined. Based on the study in Denmark and Sweden, Parkin estimated that 90% of Anal cancers are attributable to HPV. - Sexual activityHuman sexual behaviorHuman sexual activities or human sexual practices or human sexual behavior refers to the manner in which humans experience and express their sexuality. People engage in a variety of sexual acts from time to time, and for a wide variety of reasons...
: Having multiple sex partners due to the increased risk of exposure to the HPV virus. Receptive anal intercourseAnal sexAnal sex is the sex act in which the penis is inserted into the anus of a sexual partner. The term can also include other sexual acts involving the anus, including pegging, anilingus , fingering, and object insertion.Common misconception describes anal sex as practiced almost exclusively by gay men...
, whether male or female, increases the chances of anal cancer sevenfold due to Human papillomavirusHuman papillomavirusHuman papillomavirus is a member of the papillomavirus family of viruses that is capable of infecting humans. Like all papillomaviruses, HPVs establish productive infections only in keratinocytes of the skin or mucous membranes...
. Those who engage in anal intercourse with multiple partners are 17 times more likely to develop anal cancer than those who don't, if their insertive partners are infected with the HPV virus. - SmokingSmokingSmoking is a practice in which a substance, most commonly tobacco or cannabis, is burned and the smoke is tasted or inhaled. This is primarily practised as a route of administration for recreational drug use, as combustion releases the active substances in drugs such as nicotine and makes them...
: Current smokers are several times more likely to develop anal cancer compared with nonsmokers. EpidemiologistEpidemiologyEpidemiology is the study of health-event, health-characteristic, or health-determinant patterns in a population. It is the cornerstone method of public health research, and helps inform policy decisions and evidence-based medicine by identifying risk factors for disease and targets for preventive...
Janet Daling, Ph.D., a member of Fred Hutchinson's Public Health Sciences DivisionFred Hutchinson Cancer Research CenterThe Fred Hutchinson Cancer Research Center, is one of the world’s leading cancer research institutes...
, and her team found that smoking appears to play a significant role in anal-cancer development that's independent of other behavioral risk factors, such as sexual activity. More than half of the anal-cancer patients studied were current smokers at the time of diagnosis, as compared to a smoking rate of about 23 percent among the controls. "Current smoking is a very important promoter of the disease," said Daling. "There's a fourfold increase in risk if you're a current smoker, regardless of whether you're 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 apoptosisApoptosisApoptosis is the process of programmed cell death that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation...
, or programmed cell death, which helps rid the body of abnormal cells that could turn cancerous. Another possibility is that smoking suppresses the immune systemImmune systemAn immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
, which can decrease the body's ability to clear persistent infection or abnormal cells.
- ImmunosuppressionImmunosuppressionImmunosuppression involves an act that reduces the activation or efficacy of the immune system. Some portions of the immune system itself have immuno-suppressive effects on other parts of the immune system, and immunosuppression may occur as an adverse reaction to treatment of other...
, which is often associated with HIVHIVHuman immunodeficiency virus is a lentivirus that causes acquired immunodeficiency syndrome , a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive...
infection. - Benign anal lesions (inflammatory bowel diseaseInflammatory bowel diseaseIn medicine, inflammatory bowel disease is a group of inflammatory conditions of the colon and small intestine. The major types of IBD are Crohn's disease and ulcerative colitis.-Classification:...
(IBD), 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.
Prevention
Since many, if not most, anal cancers derive from human papillomavirusHuman papillomavirus
Human papillomavirus is a member of the papillomavirus family of viruses that is capable of infecting humans. Like all papillomaviruses, HPVs establish productive infections only in keratinocytes of the skin or mucous membranes...
infections, and since the HPV vaccine
HPV vaccine
The human papilloma virus vaccine prevents infection with certain species of human papillomavirus associated with the development of cervical cancer, genital warts, and some less common cancers...
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.
At 22 December 2010, FDA has approved Gardasil vaccine 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.
Screening
Anal Pap smearAnal Pap smear
An anal Pap smear is the anal counterpart of the cervical Pap smear. It is used for the early detection of anal cancer. The Human papilloma virus , the cause of anogenital warts, can cause anal carcinomas to form. Individuals with a history of anal warts are at risk of getting anal cancer.-...
s similar to those used in cervical cancer
Cervical cancer
Cervical cancer is malignant neoplasm of the cervix uteri or cervical area. One of the most common symptoms is abnormal vaginal bleeding, but in some cases there may be no obvious symptoms until the cancer is in its advanced stages...
screening have been studied for early detection of anal cancer in high-risk individuals.
Localised disease
Localised disease (carcinoma-in-situ) and the precursor condition, anal intraepithelial neoplasia (anal dysplasia or AIN) can be ablated with minimally invasive methods such as Infrared Photocoagulation. (Goldstone, SE, Kawalek, AZ, Huyett, JW "Infrared Photocoagulator: A useful tool for treating anal squamous intraepithelial lesions". 2005. Diseases of the Colon & Rectum 58(5), 1042-1053.Anal cancer is most effectively treated with surgery, and in early stage disease (i.e., localised cancer of the anus without metastasis
Metastasis
Metastasis, or metastatic disease , is the spread of a disease from one organ or part to another non-adjacent organ or part. It was previously thought that only malignant tumor cells and infections have the capacity to metastasize; however, this is being reconsidered due to new research...
to the inguinal
Inguinal
In human anatomy, the inguinal region refers to either the groin or the lower lateral regions of the abdomen. It may also refer to:* Conjoint tendon, previously known as the inguinal aponeurotic falx, a structure formed from the transversus abdominis insertion into the pecten pubis* Granuloma...
lymph nodes), surgery is often curative. The difficulty with surgery has been the necessity of removing the anal sphincter, with concomitant fecal incontinence
Fecal incontinence
Fecal incontinence is the loss of regular control of the bowels. Involuntary excretion and leaking are common occurrences for those affected. Subjects relating to defecation are often socially unacceptable, thus those affected may be beset by feelings of shame and humiliation...
. For this reason, many patients with anal cancer have required permanent colostomies
Colostomy
A colostomy is a surgical procedure in which a stoma is formed by drawing the healthy end of the large intestine or colon through an incision in the anterior abdominal wall and suturing it into place. This opening, in conjunction with the attached stoma appliance, provides an alternative channel...
.
In more recent years, physicians have employed a combination strategy including chemotherapy
Chemotherapy
Chemotherapy is the treatment of cancer with an antineoplastic drug or with a combination of such drugs into a standardized treatment regimen....
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
Chemotherapy
Chemotherapy is the treatment of cancer with an antineoplastic drug or with a combination of such drugs into a standardized treatment regimen....
and radiation. Biopsies to document disease regression after chemotherapy
Chemotherapy
Chemotherapy is the treatment of cancer with an antineoplastic drug or with a combination of such drugs into a standardized treatment regimen....
and radiation were commonly advised, but are not as frequent any longer. Current chemotherapy
Chemotherapy
Chemotherapy is the treatment of cancer with an antineoplastic drug or with a combination of such drugs into a standardized treatment regimen....
active in anal cancer includes cisplatin
Cisplatin
Cisplatin, cisplatinum, or cis-diamminedichloroplatinum is a chemotherapy drug. It is used to treat various types of cancers, including sarcomas, some carcinomas , lymphomas, and germ cell tumors...
and 5-FU. Mitomycin
Mitomycin
The mitomycins are a family of aziridine-containing natural products isolated from Streptomyces caespitosus or Streptomyces lavendulae. One of these compounds, mitomycin C, finds use as a chemotherapeutic agent by virtue of its antitumour antibiotic activity. It is given intravenously to treat...
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 chemotherapyChemotherapy
Chemotherapy is the treatment of cancer with an antineoplastic drug or with a combination of such drugs into a standardized treatment regimen....
. 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
Doxorubicin
Doxorubicin INN is a drug used in cancer chemotherapy. It is an anthracycline antibiotic, closely related to the natural product daunomycin, and like all anthracyclines, it works by intercalating DNA....
, 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:- T1 – 86 percent
- T2 – 86 percent
- T3 – 60 percent
- T4 – 45 percent
- N0 – 76 percent
- Node-positive – 54 percent
External links
- American Cancer Society - Detailed Guide: Anal Cancer
- Anal Warts, Anal Cancer, and Anal Pap Smears
- Anal Cancer and HPV in Men Who Have Sex With Men
- Clinically reviewed anal cancer information for patients, from Cancer Research UKCancer Research UKCancer Research UK is a cancer research and awareness charity in the United Kingdom, formed on 4 February 2002 by the merger of The Cancer Research Campaign and the Imperial Cancer Research Fund. Its aim is to reduce the number of deaths from cancer. As the world's largest independent cancer...
- National Cancer Institute (U.S.): Anal Cancer: Information for Health Professionals
- Cancer.Net: Anal Cancer
- The HPV and Anal Cancer Foundation