Topics in Gynecology - HPV and Cervical Cancer Risk
Human Papilloma Virus in Women's Health
Who would imagine that a virus was the cause of certain types of cancer? It’s beyond conjecture now because research has shown that the connection is definite. Human papilloma virus, or HPV for short, has been identified as the major player in cervical cancer, and women all over the world can benefit from new knowledge about this most common sexually transmitted disease. For many years, medical researchers have known about the connection between HPV and cancer, but until recently, there was little ability to impact the disease process. Now, with a targeted vaccine to immunize against specific strains of HPV known to be most responsible for cervical cancer, there is finally a weapon with which to fight. But what is this virus exactly, and why will a vaccine decrease the incidence of cervical, vaginal and vulvar cancers?
HPV is actually a group of common skin viruses of which there are over 100 known strains. Most people are familiar with plantar warts, and these are caused by a specific HPV strain. Genital warts are caused by at least four different strains, and cervical cancer is linked most strongly with two particular strains, HPV 16 and 18. These are known as “high risk” forms of the virus, and they are the specific targets of the currently available vaccines.
The virus is passed from person to person through skin-to-skin contact, and the cervix is particularly vulnerable to attack. Once the virus injects its DNA into the cervical cells, a sequence of events can lead, over months to years, to precancerous changes. These changes can only be detected on a Pap test or cervical biopsy, but the changes are otherwise silent. There is no telltale vaginal discharge or pain to herald the viral activity, and therefore, both male and female partners are generally unaware of its presence. Condoms are not fully protective since there is incomplete coverage of all potentially vulnerable genital skin.
In some cases, the virus does not become active right away and can literally hide inside the cells. There are known risk factors such as smoking or immunosuppression that can hasten (and worsen) the viral effects, but for the most part, it seems random as to which individuals will express the HPV changes and when.
The two commercially available HPV vaccines ideally target young males and females before they become sexually active. It would not be effective enough to only vaccinate girls and women; however, females definitely bear the brunt of the adverse affects of this infection. Health care providers will need to counsel patients regarding the limitations of these vaccines including the fact that they will not prevent any other sexually transmitted diseases such as HIV. There would the need for several injections required over the course of months similar to the hepatitis B vaccine in order to confer immunity, but the effort will be well worth it.
Approximately 60 to 80 percent of Americans have been/will be infected with HPV by age 50; however, only a very small percentage of women will develop cervical disease. Most of those, perhaps as many as 90%, will consist of mild changes that are cleared by the immune system over the course of a few years. That leaves 10% of women who can develop persistent disease that may progress to severe precancerous changes and ultimately to cervical cancer.
Women with a history of multiple sex partners, sexual activity at a young age, smoking, poor nutrition and substance abuse have a higher propensity to develop HPV infection and cervical disease. The effect of multiple partners is obvious, but the relationship of tobacco use and the development of cervical disease are complex and relates to damaged DNA. But even with the elimination of all the known risk factors, it only takes one sexual partner to impart a high-risk strain. For this reason, all women should avail themselves of the simple screening tool known as the Pap test.
Since it’s development in the late 1940’s, the Pap test has certainly saved many lives from invasive cervical cancer. It meets all the criteria for a great screening test including affordability, sensitivity to disease detection and specificity to cervical cell abnormalities. The Pap test has become a routine part of a woman’s GYN exam, and over the years, more accurate methods of specimen collection and analysis have been developed. Still, like any test, it has occasional lapses in accuracy, so putting it off for years at a time is unwise.
The exact interval of screening and when to start screening may vary slightly from woman to woman depending upon her individual risk factors. All women should begin screening at age 21 but not before. This is a relatively new recommendation based on the fact that cervical cancer is extremely rare in women younger than age 21 and testing too early leads to overly aggressive treatment for a precancerous disease process that will ultimately resolve on its own with time in this age group.