The ABCs of cervical health boil down to three other letters: HPV. There are more than 150 types of human papillomavirus (HPV), which are classified as one of the most common sexually transmitted diseases in the world. Most HPVs are cleared by the immune system before they become problematic, but some strains are known to cause genital warts and cancers.
“About 15 HPV types can cause precancerous or cancerous changes in cells,” explains Dr. Jill Powell, a SLUCare obstetrician/gynecologist. “About 99 percent of cervical cancer is caused by HPV, but it is important to know that only from 3 to 10 percent of HPV infections lead to an abnormal (cervical cancer screening test) and even fewer lead to precancerous or cancerous changes in cells. So HPV is necessary but not sufficient to cause cervical cancer. There are likely multiple factors that can lead to an HPV infection progressing to precancerous changes (dysplasia) of the cervix including smoking, a weak immune system and even genetics.”
Physicians emphasize the importance of the HPV vaccine, the only vaccine currently known to prevent cancer. “The HPV vaccine (Gardasil) is effective against four strains of HPV, including types 16 and 18 that cause more than 70 percent of the cancers,” says Dr. David Weinstein, chief of obstetrics/gynecology at Missouri Baptist Medical Center. The vaccine is approved for both boys and girls between the ages of 9 and 26 in the United States, he notes. In addition to Gardasil, Cervarix targets only types 16 and 18 and is approved for girls ages 9 to 25. The vaccines are designed to be given in three doses during a six-month period and are recommended at age 11 or 12.
“The acceptance of vaccinating teen girls has gradually grown over the years as both pediatricians and parents become more informed about the important health benefits of HPV vaccination,” Powell says. “Now that HPV vaccination is approved for boys, I think that vaccination rates universally will increase as it becomes a more routine teen vaccine rather than gender-specific. I have personally had my own teenage son vaccinated and am planning for my daughter to be vaccinated at that age also.”
Weinstein adds that the benefits of the HPV vaccine already are becoming evident. “There already has been a reduction in precancerous cells,” he says. “In Australia, where they’re vaccinating both boys and girls, there’s been a very significant reduction in the risk of cervical cancer and precancerous cells in females.”
The other primary defense against cervical cancer is screening, known as pap testing, to identify precancerous cells. If identified, the cells can be removed or treated and cancer prevented.
“Cervical cancer screening recommendations have changed significantly over the past few years because of advances in pap smear technology and accuracy, advances in HPV testing to better predict whether an abnormal pap smear could lead to cervical cancer, and more research about the natural history of HPV infection and its subsequent clearance or persistence,” Powell says.
Current recommendations call for screening tests to begin at age 21, regardless of sexual activity prior to that time. “(Women) still should receive at least annual testing on a pelvic exam or urine sample for chlamydia infection, but a pap smear should not be done (annually) because cervical cancer is exceedingly rare in this age group, and screening has not been shown to decrease these rates,” Powell adds.
Women ages 21 to 29 should have a screening test every three years, and women ages 30 to 64 can have a pap test along with HPV testing, known as ‘co-testing,’ every five years or a pap test alone every three years. At age 65, most women who have had at least three negative pap tests during the last 10 years or two negative pap tests with negative HPV testing during the last 10 years and have not had moderate or severe cervical dysplasia or cervical cancer in the past need no further testing.
Powell envisions a future where cervical cancer is all but obliterated: “With the combination of appropriate screening and now HPV vaccination, my hope is that in 25 years, I have to explain to my medical students what cervical cancer looks like and describe the surgeries we use to do to treat it because they will see it so infrequently.”