Despite the availability of a vaccine that guards against human papillomavirus (HPV), common misconceptions still linger about HPV and its link to certain cancers.
Ashley Haggerty, MD, a gynecologic oncologist at the Hospital of the University of Pennsylvania, reminds patients that HPV is not one virus but a group, and that not all of them are linked with cancer.
"HPV is actually about 40 viruses transmitted sexually, and they're so common that over 80 percent of adults will have some kind of HPV exposure in their lifetime," she explains. "Of the many strains that exist, about 10 are linked with an increased risk of certain kinds of cancers."
Two strains in particular, HPV-16 and HPV-18, account for the majority of cervical cancer cases caused by HPV infection. Most people naturally clear HPV from their bodies, because their immune systems recognize and destroy the virus. But for a small subset who are unable to clear it, the virus can trigger changes at the cellular level.
These changes happen in epithelial cells, which are found in certain areas of the body, including the cervix, vulva, anus, and parts of the throat. When HPV reaches one of these cells, the virus can cause it to grow too much and not die off. These changes are known as dysplasia, which can cause cancer if it persists for a long time.
"Dysplasia doesn't automatically lead to cancer," Dr. Haggerty says. "Some types of HPV cause low-grade dysplasia, meaning these people are at a very low risk of cancer. The danger is higher for women who have the high-risk types of HPV."
Preventing HPV
Because some types of HPV can lead to cancer, vaccination is recommended for males and females ages 9-26. The vaccine protects against seven of the most common cancer-causing types of HPV and two kinds that cause genital warts.
"If we prevent HPV infections, we can reduce one of the causes of these cancers," Dr. Haggerty explains. "Unfortunately, the United States has not been great at vaccinating against HPV. Countries like Australia that have higher vaccination rates have shown a significant reduction in dysplasia and thus lower rates of these cancers."
Though a three-dose vaccination schedule is still recommended, the Centers for Disease Control found that a two-dose vaccination schedule likely gives the same amount of immune protection as the recommended three doses.
Dr. Haggerty reminds patients that the vaccine has been extensively tested to ensure its safety. And parents should consider the potentially life-saving benefits when broaching the subject with their children.
"Some people assume that because HPV is a sexually transmitted virus, vaccination necessitates an awkward or difficult conversation," she says. "We have spent billions of dollars finding better ways to fight cancer. Now we have a vaccine that we know prevents certain kinds of cancers, so we need to be practical about vaccinating those who are eligible."
Screening for Cancer
For those beyond the age of HPV vaccination, safe sexual practices and regular cancer screenings are recommended for managing the risk of genital cancers.
Cervical cancer screening includes a Pap test, which detects abnormal cells in the cervix that may develop into cancer. Other tests can look for the high-risk types of HPV in cervical cells.
Women ages 21 through 29 should receive a Pap test every 3 years, and women 30 to 65 should receive a HPV test and a Pap test every 4 to 5 years, or a Pap test alone every 3 years.
Those with certain immune-system deficiencies may need to be screened more frequently, and women who have had a hysterectomy do not need to have cervical screening unless the surgery was done to treat a precancerous lesion or cancer in the cervix.