HPV Vaccine Prevents Most Cervical Cancers and Genital Warts

A new vaccine gives doctors a powerful tool that, at least in the US, could dramatically change the way cancers of the cervix are diagnosed and treated. The vaccine, sold under the brand name Gardasil, was given the US Food and Drug Administration (FDA) go-ahead for widespread use in June 2006.

"The vaccine is for four of the more than 100 known types of HPV," said HPV prevention and treatment expert Fredrik F. Broekhuizen, MD, Medical College of Wisconsin Professor of Obstetrics & Gynecology. "Two of them, Types 6 and Type 11, are 'low risk' and the most common reasons for having genital warts. The other two types, 16 and 18, are 'high risk' and responsible for seventy percent of all the cervical pre-cancer conditions and cervical cancer. That's why vaccination with those types will have a lot of impact on how many patients will have genital warts and on how many patients will have pre-cancer and cervical cancer."

The FDA used a priority process to get the vaccine on the market as quickly as possible, hailing it as a major advancement in public health. The vaccine is approved for use in females age 9 to 26 and is given in three injections over a six-month period. Several large-scale studies have shown that Gardasil virtually eliminates the adverse health effects of HPV Types 6, 11, 16, and 18.

Millions Infected
More than 6.2 million Americans become infected with genital HPV each year and over half of all sexually active men and women become infected at some time in their lives, according to estimates by the Centers for Disease Control and Prevention (CDC). On average, CDC reports, there are 9,710 new cases of cervical cancer and 3,700 deaths attributed to it in the US each year. Worldwide, cervical cancer is the second most common cancer in women, estimated to cause over 470,000 new cases and 233,000 deaths each year.

"Women are more often symptomatic than men," says Dr. Broekhuizen. "But the cancer-causing HPV types can cause problems in men, too, such as anal cancer and penile cancer. Still, given a similar rate of exposure to the high risk HPV types, the number of men that will develop pre-cancers or cancerous lesions is much lower than the number of women. Women are far more vulnerable to the effects of the HPV virus, and that's true on both the cancer side and the genital warts side.

"Warts are small growths that can occur on any part of the body. There are different types of warts, all caused by viruses that are in the same 'family' of papillomaviruses. There are genital warts and then there are warts such as those on the fingers or other parts of the body. Those viruses are related and have similar physical manifestations. Gynecologists usually deal with genital warts." ("Papilloma" is a benign tumor such as a wart due to overgrowth of certain tissue; "papillomavirus" is the virus that causes the papilloma.)

"The low-risk HPV viruses only cause genital warts. Quite often, the immune system will make those warts spontaneously disappear, and we have many medications to help make them disappear. As a nuisance, the warts can make patients very upset, but there is no significant long-term harm.

"We are less concerned about genital warts themselves and much more concerned about those types of viruses that can cause pre-cancerous changes in the vulva, the vagina, and specifically the cervix," said Dr. Broekhuizen. "Another vaccine will be coming on the market within the next year or so that protects against Types 16 and 18 (the types most associated with cervical cancers) but not against Types 6 and Type 11 (typically responsible for genital warts).

"When discussing the high-risk types of HPV, I think a lot of people don't realize that being exposed does not necessarily mean that you get cancer. Out of every 100 patients who are exposed to high-risk HPV, less than one person will develop pre-cancer and cancer. And again, our immune system will, in most patients, suppress the manifestations of the disease."

Dr. Broekhuizen noted that the majority of patients exposed to any HPV virus will never know that they were exposed. A small percentage will have some symptoms, like having genital warts or having an abnormal Pap smear, he said, and it is a very small percentage that will actually have persistent presence of the virus that then leads to pre-cancer and cancer.

Explaining, and Beating, the Odds
"If you look at risk from the perspective of who is more at risk for getting the virus, that's fairly easy to define. In up to 90% of patients, exposure to HPV is the result of sexual activity. This does not require intercourse - the virus is spread through skin contact. Exposure to multiple sex partners leads to higher risk of getting the virus. Research studies that have looked at sexually active patients in their 20s have concluded that probably 80% of the population, at some time in their lives, will have been exposed to HPV. That makes HPV itself not only a disease, but almost part of the human condition."

But HPV is not a true STD (sexually-transmitted disease), notes Dr. Broekhuizen, because it is not spread through exchange of bodily fluids, but by skin contact. In fact, research studies indicate that HPV can be present in up to 10% of 5-year-olds. This is not a result of sexual activity. Typically, the virus was transmitted to the child from the mother during birth. The virus can even be transmitted by caregivers who are less than thorough in matters of hygiene - if a person who already has HPV does not wash their hands after using the bathroom, and then takes care of a child, the possibility for spreading the disease exists.

Development of vaccines for cervical cancer and genital warts reflects an increased understanding of how HPV works, said Dr. Broekhuizen. He added that the ongoing refinement of prevention and treatment concepts in recent years has led to better ways to eliminate genital warts and to a steady decrease in cervical cancer deaths in the US, where tools such as pap smears and other tests for cervical cancer have been available for a long time.

One of the great challenges facing health care practitioners dealing with HPV is explaining to patients that, while the overall likelihood of getting cervical cancer may be statistically slight in the US, the presence of high-risk HPV increases that risk almost astronomically as compared to risk factors for other cancers.

As an example, "If you have a the Type 16 strain of the virus, your risk of getting cervical cancer is 434 times higher than if you do not have a high-risk HPV type," said Dr. Broekhuizen. "Having this risk factor doesn't mean you're going to get cervical cancer, but 434 times is an enormous increase in risk. As a comparison, smokers have an 8 times higher risk of lung cancer than nonsmokers. Estrogen therapy may increase your risk of breast cancer by 1.3 times. Given how 434 compares with 8 or 1.3, the impact of what we can do with this vaccine is enormous."

Dan Ullrich
HealthLink Contributing Writer

Dr. Fredrik Broekhuizen practices at the Froedtert & The Medical College of Wisconsin Obstetrics and Gynecology Clinic and the Children's Hospital of Wisconsin Maternal-Fetal Care Center.

For more information on this topic, see the second part of Dr. Broekhuizen's article, HPV Vaccine Offers Cancer Protection, But for How Long?

MCW Health News presents up-to-date information on patient care and medical research by the physicians of the Medical College of Wisconsin.