HPV: The Potentially Cancerous STD
Human papillomavirus (HPV), the virus strongly linked to cervical cancer, is one of the most common sexually transmitted diseases (STDs). What makes it different from other STDs is its widespread prevalence.
Two years ago, 22-year-old Cindy went in for her yearly pap smear. She endured the usual stress of the vaginal and cervical exam, and went home thinking nothing of it. When her gynecologist told her that her pap smear had come back abnormal with possible mild dysplasia and human papilloma virus (HPV)-associated changes, she was surprised, to say the least. Cindy had never heard of HPV, which is the virus that causes genital warts. Even more disconcerting was the fact that some strains of HPV are linked to cervical cancer. Since both her parents had died of cancer within the last three years, she was afraid that this condition would progress into cancer, too.
HPV most commonly causes genital warts. One million new people each year get HPV-related genital warts: small flat or raised areas on the genital skin (but often located in places hard to see without a specialized medical examination). This is in addition to the estimated 24 million who already suffer from them, according to the National Institute of Allergy and Infectious Diseases. Researchers estimate that, like Cindy, even more people contract HPV and never develop the warts.
Especially when acquired in early adolescence, HPV seems to eventually disappear from the body and may cause neither warts nor cancer. But in some women, HPV does cause cervical cancer, and this disease still leads to more than 2000 deaths in the US every year. Evidence of prior infection with HPV (usually Type 16 or 18) can be found in most women with cervical cancer. While relatively few women infected with HPV (even the cancer-causing types) ever develop cancer, many—like Cindy—do develop abnormal Pap smears that could lead to cancer if untreated. And, also like Cindy, many women have still never heard of HPV.
What Is HPV?
HPV is a virus, which means it is an organism that must live inside human cells and is far too small to be seen by the human eye, or even a microscope. Once inside a skin cell, HPV grows actively and may “integrate” itself into the cell’s DNA. There are many types of HPV, some of which cause only warts and some of which are associated with cancer or pre-cancerous Pap smear changes. Warts may appear on or in the vagina, cervix, penis, urethra, or anus. They are usually flesh-colored bumps, appearing alone or in cauliflower-like clusters. Most are painless, though some are painful, itchy, or both.
But most HPV types cause invisible warts or no warts at all. Some "subclinical" (undetected) infections surface as dysplasia (abnormal cells) on a pap smear. While men are commonly infected, they don’t seem to suffer serious consequences, even from the cancer-causing types like HPV 16 and 18. Only rarely have these viruses been identified in cases of penile cancer, itself a very rare cancer.
How Is HPV Spread?
Unlike most sexually transmitted diseases, HPV travels via skin, especially genital contact, and not via blood or body fluids. Transmission risk is high. One study at the University of Washington found HPV in 80% of people with a lifetime history of less than five sex partners. Even a condom isn't entirely protective because it leaves bare the vulva, anus, scrotum, and penis. It's also possible for pregnant women to pass HPV to their babies during delivery. Long-term studies are underway to clarify the extent and seriousness of this risk.
With HPV, like many other STDs, being symptom-free doesn't mean that it's entirely safe to have sex without risk of transmission. Even if the warts can't be seen or aren't present, HPV can still be contagious.
Does HPV Mean Cancer?
HPV is not synonymous with cancer. Though certain subclinical types of HPV turn up in most cervical cancers, the wart-forming types almost never cause cancer. Both high- and low-risk types of the virus can cause abnormal pap smears, but cancer is a rare event and can almost always be prevented by following guidelines for frequent Pap smears.
In addition to HPV, behaviors like smoking, multiple sex partners, and having sex at a young age also possibly heighten the risk of cervical cancer.
How Would I Know If I Have HPV?
Genital warts are clear evidence of HPV. Otherwise, most people never know for certain that they have the virus unless they have an abnormal Pap smear or a positive DNA test for the HPV virus. The optimal use of HPV DNA testing has yet to be defined. It likely has value as follow-up for some kinds of Pap smear abnormality and may even be valuable when done along with a Pap smear in women older than 30. HPV DNA testing in younger women is controversial because in many of these individuals the virus will disappear spontaneously, apparently leaving no residual increased risk of cancer.
After an abnormal pap smear, a presumptive diagnosis of HPV can be made by looking at the cervix through a microscope-like device called a colposcope. Signs of the virus, like tiny warts or tissue patterns suggestive of dysplasia, are noted. A biopsy is often done as well to look for changes suggesting current or future cancer risk. The management of mildly abnormal Pap smears may vary among medical providers. Some choose to perform immediate colposcopy, others may repeat Pap smears, or perform viral DNA testing. Still other practitioners choose not to do this right away, opting to wait six months to do a second pap smear. The legitimate rationale for such delay is that early dysplasia often spontaneously disappears; and the chance of rapid change to cancer is remote.
Researchers estimate that 90% of all abnormal pap smears are associated with human papillomavirus DNA.
How Are HPV-Induce Warts Treated?
A variety of treatments do exist for visible warts, and scientists are investigating whether vaccination might lead to regression or even a cure.
Between 10%-30% of warts regress spontaneously, but physicians cannot predict those that will regress. Topical ointments are also available for treatment. Podofilox (Condylox) uses an active ingredient found in another anti-wart medication, podophyllin (Podofin, Pod-Ben 25), which is made from the resin of the mandrake tree.
A topical treatment applied three times a week, imiquimod 5% (Aldara), has shown promise in treating genital warts. In two clinical trials, at least 50% of patients receiving this treatment had a complete clearance of their warts. After the trials were over and patients entered a 12-week imiquimod-free period, the recurrence rates were low. According to one of the researchers associated with the trials, the benefit of imiquimod lies with the fact that it is well tolerated in comparison with other medications and therapies. Trichloroacetic acid is another skin treatment sometimes used, but it is very caustic and some studies have found it ineffective.
If other treatments fail and the patient is otherwise healthy, interferon-alpha (Alferon N, Intron A) can be used. The drug is injected into genital warts two or three times weekly for about eight weeks. It is very expensive and has a high incidence of unpleasant side effects. An injectable gel (Accusite) containing the anti-cancer drug fluorouracil (5-FU) is proving to be safe and effective for genital warts. Other experimental drugs include afovirsen, which blocks HPV from using its own genes, and GS504, which may block the virus from replicating.
Perhaps most commonly, HPV warts can also be treated using cryosurgery with liquid nitrogen or surgically using conventional procedures or carbon dioxide laser. Until scientists perfect ways to specifically target and kill the virus, no treatment is foolproof. Although warts can be removed, microscopic HPV infection will still be present. Although warts may disappear on their own, many researchers support wart removal because it, theoretically, could reduce transmission risk and perhaps help people feel better about their condition.
How Can I Reduce My Risk of HPV?
Limiting sexual activity to a relationship in which neither partner has ever had intimate physical contact with another person (since the virus can be spread by skin-to-skin contact, intercourse is not essential for transmission) will likely prevent acquisition of HPV. Otherwise, virtually every man and woman who is sexually active is at risk for HPV, though fortunately, few suffer serious consequences as a result. Condoms are recommended because they can prevent many types of sexually transmitted diseases, although their use does not guarantee protection from HPV. If you are in a monogamous relationship and your partner does not have the virus, you are not likely to get it. In the absence of a practical screening test, indiscriminate sex can be a gamble.
A vaccine for HPV has been released that is currently recommended for all women at about the age of 11. This vaccine will primarily prevent infection with the cancer-causing types of HPV, so it will not eliminate genital wart disease (or even all abnormal Pap smears). It is very likely, however, that this vaccine will greatly reduce the risk of developing cervical cancer for the next generation of women. Unfortunately, the current vaccine has reduced preventive effectiveness when given to women who have previously been exposed to HPV. Talk with your doctor to learn more about this vaccine.
The American College of Obstetricians and Gynecologists
Centers for Disease Control and Prevention
National Cancer Institute
National Institute of Allergy and Infectious Diseases
Sex Information and Education Council of Canada
The Society of Obstetricians and Gynaecologists of Canada
McNeil C. Search for HPV treatment vaccine heats up, researchers optimistic. J Natl Cancer Inst. 2006;98(14):954-955.
Last reviewed June 2008 by Ganson Purcell Jr., MD, FACOG, FACPE
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