Gerald Hurowitz, M.D.·Published 5 April 2012·7 min read
Key points
People who've ever had genital warts may have a somewhat higher risk of several types of cancer - possibly including common skin cancers, a new study suggests.
Genital warts, which are also known as “venereal warts”, are a highly contagious disease that is transmitted sexually.
For the study, Kjaer and her colleagues looked at medical records for nearly 33,000 women and 16,000-plus men diagnosed with genital warts over 30 years.
These cells, which are organized in layers, cover the inside and outside surfaces of the body, including the skin, the throat, the genital tract, and the anus.
People who've ever had genital warts may have a somewhat higher risk of several types of cancer - possibly including common skin cancers, a new study suggests.
The findings, reported in the Journal of Infectious Diseases, confirm some well-established connections between the genital warts virus and certain cancers. And they hint that there could be additional risks.
Genital warts are caused by certain strains of the human papillomavirus (HPV). It's well known that some of those HPV strains - some of which are the focus of vaccines - can also promote tumors.
In most people, the immune system is able to clear HPV infection fairly quickly. But some people harbor persistent infections, and a chronic infection with a cancer-linked strain can eventually lead to cancer in some cases.
HPV is probably best known as a cause of cervical cancer - a disease that experts say is nearly always caused by HPV. The virus is also blamed for most cases of anal cancer, and a large share of vaginal, vulvar and penile cancers.
Lesser known is the link between HPV and certain cancers of the mouth and throat. But a number of studies have found that a large portion of those cancers can be traced to HPV infection.
Genital warts and risk of cancer – a Danish study of nearly 50,000 patients with genital warts
Conclusions Individuals with GW have a long-term increased risk of anogenital cancers and head and neck cancers. The elevated risks of non-melanoma skin cancers might indicate an association with HPV, while excess risks of other cancers could point to differences in other risk factors between individuals with GW and the general population.
Maria Blomberg, Soren Friis, Christian Munk, Andrea Bautz and Susanne K. Kjaer
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Published by Oxford University Press on behalf of the Infectious Diseases Society of America.
These latest findings, from a study of more than 49,000 Danish adults, confirm all those connections, said Dr. Susanne Kruger Kjaer of the Danish Cancer Society, who worked on the study.
What are Genital Warts?
Genital warts, which are also known as “venereal warts”, are a highly contagious disease that is transmitted sexually. The disease is caused by various forms of human papillomavirus (HPV). 90 percent of all cases of genital warts are caused by types 6 and 11 of HPV. Most of the people who get these two strains never develop any symptoms and visible warts. HPV may also cause cervical cancer. Around 70 percent of cervical cancer cases result from types 16 and 18. The strains, however, of HPV that bring about genital warts are not related to the ones that cause cervical cancer.
Written and revised by
Gerald Hurowitz, M.D.
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Genital warts are small cauliflower-shaped bumps that are flesh-colored. They are often as tiny as 2 millimeters in diameter, but they can grow in clusters and expand into large masses in the genital region.
They also hint that HPV might be involved in the risk of non-melanoma skin cancers - the most common, and highly curable, types of skin cancer.
CANCER IN LESS THAN FIVE PERCENT
For the study, Kjaer and her colleagues looked at medical records for nearly 33,000 women and 16,000-plus men diagnosed with genital warts over 30 years.
What is the association between HPV infection and cancer? High-risk HPV infection accounts for approximately 5 percent of all cancers worldwide . However, most high-risk HPV infections occur without any symptoms, go away within 1 to 2 years, and do not cause cancer. These transient infections may cause cytologic abnormalities, or abnormal cell changes, that go away on their own.
Some HPV infections, however, can persist for many years. Persistent infections with high-risk HPV types can lead to more serious cytologic abnormalities or lesions that, if untreated, may progress to cancer.
As expected, they had higher-than-average rates of cervical, anal, penile and vaginal cancers, as well as certain mouth and throat cancers.
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The vast majority remained cancer-free during the study period. In all, 2,363 people - or less than 5 percent of the study group - developed some form of cancer. And only 305 were diagnosed with any of the cancers known to be linked to HPV.
Still, some of those risks were higher than average.
Men with a history of genital warts had a 21 times higher-than-average risk of anal cancer, for instance. Among women, the risk was eight times higher than the norm.
How do high-risk HPVs cause cancer?
HPVs infect epithelial cells. These cells, which are organized in layers, cover the inside and outside surfaces of the body, including the skin, the throat, the genital tract, and the anus. Because HPVs are not thought to enter the blood stream, having an HPV infection in one part of the body should not cause an infection in another part of the body.
Once an HPV enters an epithelial cell, the virus begins to make proteins. Two of the proteins made by high-risk HPVs interfere with normal functions in the cell, enabling the cell to grow in an uncontrolled manner and to avoid cell death.
Many times these infected cells are recognized by the immune system and eliminated. Sometimes, however, these infected cells are not destroyed, and a persistent infection results. As the persistently infected cells continue to grow, they may develop mutations that promote even more cell growth, leading to the formation of a high-grade lesion and, ultimately, a tumor.
Researchers believe that it can take between 10 and 20 years from the time of an initial HPV infection until a tumor forms. However, even high-grade lesions do not always lead to cancer. The percentage of high-grade cervical lesions that progress to invasive cervical cancer has been estimated to be 50 percent or less.
The rates of cervical, penile, vaginal, and mouth and throat cancers were anywhere from 50 percent to eight-times higher, compared with the general population.
There was also some evidence tying genital warts to non-melanoma skin cancers, the researchers say.
Overall, 440 study participants, or less than 1 percent, developed non-melanoma skin cancer - which is somewhat higher than expected, the researchers say.
Complications of HPV Certain strains of HPV are associated with a number of serious health risks. In particular, some HPV strains appear to increase your risk of developing specific types of cancers, including vulvar, penile, and cervical cancer. Women with prolonged HPV infection are at particular risk for developing cervical cancer. In fact, more than 80% of women with cervical cancer have a history of HPV infection. For this reason, it is essential that every woman who is sexually active have regular pap smears. The pap smear can help detect any irregular cells in the cervix. With early detection, the vast majority of cervical cancer sufferers can be treated. It is important to note, though, that those HPV strains associated with cervical cancer generally do not cause any outward symptoms and rarely are associated with genital warts.
HPV and Pregnancy
HPV infection can also prove problematic during pregnancy. The strains of HPV that cause genital warts are particularly problematic, because genital warts can grow to large sizes during pregnancy. These large genital warts can make urination difficult or they can sometimes block the birth canal during delivery. This can necessitate a cesarean section delivery. Rarely, babies contract genital warts during the delivery process. Genital warts can develop in the throats of these babies, making breathing difficult. This can be potentially life-threatening and requires immediate treatment.
It's possible there is some type of connection between HPV and non-melanoma skin cancer, Kjaer told Reuters Health in an email. Since the immune system fights both infections and cancer, it's possible that impaired immune function could underlie persistent HPV infection and skin cancer in some people.
But that's all "speculative" for now, Kjaer stressed.
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Non-melanoma skin cancers are the most common type of cancer by far. In the U.S., about 3.5 million cases are diagnosed each year, according to the American Cancer Society.
Experts say the best way to cut your risk of skin cancer is to limit your sun exposure, especially if you have fair skin. No one knows whether preventing HPV infection has any effect.
COULD VACCINES PLAY A ROLE?
For now, there are no "concrete practical implications" from the current findings, Kjaer said.
But if further studies confirm that HPV is associated with a broader range of cancers, that could underscore the importance of preventing the infection, according to Kjaer.
There are two vaccines that can prevent infection with certain cancer-related strains of HPV: Merck's Gardasil and GlaxoSmithKline's Cervarix, both of which cost about $400 for three doses. The current study was funded by Sanofi Pasteur, which sells Gardasil in Europe.
Right now, public health authorities recommend that all girls and boys ages 11 and 12 receive the HPV vaccine. Older girls and young women up to age 26 are advised to get "catch-up" shots if they've never been vaccinated. The same advice goes for boys and men ages 13 to 21.
The HPV vaccine is generally considered safe. The most common side effects are pain at the injection site, fever, dizziness and nausea, according to the U.S. Centers for Disease Control and Prevention.
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