What are the risk factors for anal cancer?
A risk factor is anything that affects your chance of getting a disease such as cancer. Different cancers have different risk factors. For example, exposure to strong sunlight is a risk factor for skin cancer. Smoking is a risk factor for cancer of the lung and many other cancers. But risk factors don't tell us everything. Having a risk factor, or even several risk factors, does not mean that you will get cancer. Also, people without risk factors can still get cancer.
Human papilloma virus infection
Most squamous cell anal cancers seem to be linked to infection by the human papilloma virus (HPV), the same virus that causes cervical cancer. In fact, women with a history of cervical cancer (or pre-cancer) have an increased risk of anal cancer.
HPV is a group of more than 100 related viruses. They are called papilloma viruses because some of them cause papillomas, which are more commonly known as warts. There are several subtypes of the virus, but the one most likely to cause anal cancer is called HPV-16. HPV-16, as well as HPV 18, HPV 31, HPV 33, and HPV 45 are considered high-risk types of HPV because they are strongly linked to cancer. They can also cause cancers of the cervix, vagina, and vulva in women, as well as cancer of the penis in men, and throat cancer in both women and men.
Other subtypes of HPV can cause warts in the genital and anal areas. The medical term for these warts is condyloma acuminatum. The 2 types of HPV that cause most cases of anal and genital warts are HPV 6 and HPV 11. They are called low-risk types of HPV because they tend to cause warts but not cancer. HPV infection can cause anal and genital warts, but most people infected with HPV do not have genital warts or any other signs of infection.
HPV is passed from one person to another during skin-to-skin contact with an infected area of the body. HPV can be spread during sex -- including vaginal intercourse, anal intercourse, and oral sex - but sex doesn't have to occur for the infection to spread. All that is needed is for there to be skin-to-skin contact with an area of the body infected with HPV. The virus can be spread through genital-to-genital contact. It is even possible for a genital infection to spread through hand-to-genital contact.
An HPV infection also seems to be able to be spread from one part of the body to another. This means than an HPV infection may start in the genitals and then spread to the anus.
It can be very hard to avoid being exposed to HPV. It might be possible to prevent genital HPV infection by not allowing others to have contact with your anal or genital area, but even then there could be other ways to become infected that aren’t yet clear.
Infection with HPV is common, and in most cases the body is able to clear the infection on its own. But in some cases the infection does not go away and becomes chronic. Chronic infection, especially when it is with high-risk HPV types, can eventually cause certain cancers, including anal cancer.
For men, the 2 main factors influencing the risk of genital HPV infection are circumcision and the number of sexual partners. Men who are circumcised (have had the foreskin of the penis removed) have a lower chance of becoming and staying infected with HPV. The risk of being infected with HPV is also strongly linked to having many sexual partners (over a man's lifetime).
In women, HPV infections occur mainly at younger ages and are less common in women over 30. The reason for this is not clear. Certain types of sexual behavior increase a woman's risk of getting a genital HPV infection, such as having sex at an early age and having many sexual partners.
Although women who have had many sexual partners are more likely to get infected with HPV, a woman who has had only one sexual partner can still get infected. This is more likely if she has a partner who has had many sex partners or if her partner is an uncircumcised male.
In a study that looked at risk factors for anal HPV infection in women, risk was increased in younger women and in those who had more than 5 sexual partners in their lifetime. Ever having anal sex also increased risk.
Circumcision and HPV: Men who have not been circumcised are more likely to be infected with HPV and pass it on to their partners. The reasons for this are unclear. It may be that the skin on the glans of the penis goes through changes that make it more resistant to HPV infection. Another theory is that the surface of the foreskin (which is removed by circumcision) is more easily infected by HPV. Still, circumcision does not completely protect against HPV infection -- men who are circumcised can still get HPV and pass it on to their partners.
Condoms and HPV: Condoms can provide some protection against HPV, but they do not completely prevent infection. One study found that when condoms are used correctly they can lower the genital HPV infection rate in women by about 70% - but they need to be used every time sex occurs. This study did not look at the effect of condom use on anal HPV infection. In another study, men who used condoms less than half of the time had a higher risk of HPV infection. Condoms cannot protect completely because they don't cover every possible HPV-infected area of the body, such as skin of the genital or anal area. Still, condoms provide some protection against HPV, and they also protect against HIV and some other sexually transmitted diseases. Condoms (when used by the male partner) also seem to help genital HPV infections clear (go away) faster in both women and men.
Other cancers
Ever having cancer of the cervix, vagina, or vulva is linked to an increased risk of anal cancer. This is likely because these cancers are also caused by infection with HPV. Although it is likely that having penile cancer, which is also linked to HPV infection, would increase the risk of anal cancer, this link has not been shown in studies.
HIV infection
People infected with the human immunodeficiency virus (HIV), the virus that causes AIDS, are much more likely to get anal cancer than those not infected with this virus.
Sexual activity
Having multiple sex partners increases the risk of infection with HIV and HPV. It also increases the risk of anal cancer.
Receptive anal intercourse also increases the risk of anal cancer in both men and women, particularly in those younger than the age of 30. Because of this, men who have sex with men have a high risk of this cancer.
Smoking
Smoking also increases the risk of anal cancer. Current smokers are several times more likely to have cancer of the anus compared with people who do not smoke. Quitting smoking will reduce the risk. People who used to smoke but have quit are only slightly more likely to develop this cancer compared with people who never smoked.
Lowered immunity
Higher rates of anal cancer occur among people with reduced immunity, such as people who have had an organ transplant and must take medicines that suppress their immune system.
Race and gender
Anal cancer is more common in African-Americans than in whites. Overall, it is more common in women than men, but in African Americans it is more common in men than in women.
http://well.blogs.nytimes.com/2011/02/09/saving-lives-from-anal-cancer/
Saving Lives From Anal Cancer
Paulette Crowther’s three children were grown and she was plotting a midlife career change when a routine colonoscopy picked up cancer, but not of the colon — of the anus.
The diagnosis was a shock. Ms. Crowther, a 51-year-old mother of three from New York City, had had no symptoms and was feeling just fine. It felt like a bolt from the blue. The cancer had already spread.
But as Ms. Crowther and her children scoured the Internet for information, they couldn’t help but wonder whether the cancer could have been prevented, or caught earlier at least.
Some 80 to 90 percent of anal cancers are caused by the human papillomavirus, or HPV, the same kind of virus that causes cervical cancer. And decades earlier, when Ms. Crowther was in her 20s, she had been treated for cervical dysplasia, a condition that often precedes cervical cancer – and is also caused by an HPV infection.
If only she had known.
“We think Mom could have been saved if she’d been monitored and screened more often,” said Ms. Crowther’s oldest child, Justine Almada, 27. “Studies show that if you have cervical dysplasia, you’re at higher risk. At the very least, she should have been made aware of that.”
She added, “Anal cancer is quite treatable if it’s found early.”
The same types of human papillomavirus implicated in cervical cancer, HPV 16 and 18, are also linked to anal cancer. And in December, the Food and Drug Administration expanded the approved uses of the HPV vaccine Gardasil to include prevention of anal cancer and precancerous lesions.
Ms. Crowther — who was fiercely devoted to the brood she raised in Lower Manhattan, largely on her own after a divorce, and whom the children call their “best friend” — died last April. Within three months, Justine and her siblings, Tristan and Camille Almada, ages 25 and 23, had established the HPV and Anal Cancer Foundation.
The foundation’s aim is to raise awareness about the link between the human papillomavirus, an incredibly common sexually transmitted infection, and a whole list of cancers, each of which affects a relatively small number of people but which, taken together, affect tens of thousands. Besides anal cancer, HPV infections are linked to some gynecological cancers, like vulvar and vaginal cancers, certain penile cancers in men and certain head and neck cancers.
With a robust Web site — analcancerfoundation.org — and an expert scientific advisory board, the organization also aims to increase awareness about preventive screening, provide support to family members and caregivers and raise money for research on treatment, which remains limited for metastatic disease.
“What keeps us going is the thought that if someone had done this already, it could have prevented what happened to Mom,” said Camille, who recently stepped in to run the tax-exempt foundation.
The irony is that while Ms. Crowther was still alive, she never told anyone what kind of cancer she had. Experts say that’s not unusual for people with anal cancer, who often are ashamed of their disease. “The assumption most people make is that if you have anal cancer, you had anal sex,” Camille said. “That’s not true. Heterosexual men also have HPV in their anus, because HPV is so prevalent. But also: who cares if you had anal sex?”
Dr. Cathy Eng, an associate professor in gastrointestinal medical oncology at M.D. Anderson Cancer Center in Houston, said: “It’s really important to emphasize that the average person is in fact a female in her late 50s, early 60s — that’s the average patient.” The actress Farrah Fawcett, of “Charlie’s Angels” fame, who documented her battle with anal cancer on film, was fairly typical; she was 62 when she died of the disease in 2009. Dr. Eng added, “People associate anal cancer in general with men who have sex with men who are H.I.V.-positive; that’s not the case.”
While men who have sex with men are at elevated risk for developing anal cancer, the disease strikes more women than men: cases are diagnosed in some 2,000 men and 3,260 women each year in the United States. The disease is on the rise, with new diagnoses increasing by 2 percent a year in both men and women, according to national cancer statistics. Each year, 720 people die of anal cancer.
Other risk factors include having a history of cervical cancer or other gynecological malignancies, having a suppressed immune system, an atypical Pap smear and testing positive for HPV 16 or 18. Having had multiple sex partners, having a history of sexually transmitted disease and having had receptive anal intercourse, even without full penetration, likewise increase risk.
Early symptoms like blood in the stool or a feeling of pressure can easily be mistaken for hemorrhoids. “An important message is: if your hemorrhoids don’t get better, you need to talk to your doctor,” Dr. Eng said.
There is no clear medical consensus on screening for anal cancer. Choices include a digital rectal exam or digital anal exam, done as part of a physical or gynecological checkup, or an anal Pap smear. Dr. Joel Palefsky, an infectious disease specialist at the University of California, San Francisco, offers a screening procedure called high-resolution anoscopy, which may be an especially sensitive screening technique. But it is not widely available.
“If a woman has had cervical cancer, she is clearly at increased risk for anal cancer,” Dr. Palefsky said. “We’ve known about the connection for a while. People didn’t pay a lot of attention until recently.”
Another of the foundation’s goals is to destigmatize the disease and end the isolation many patients feel. “When you have cancer, you shouldn’t be ashamed of it; it’s terrible enough to have cancer,” Camille said.
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