In recent years, recommendations for cervical cancer screenings have gone from once a year to once every three to five years for most women. Now, Harvard researchers suggest that women who are vaccinated against human papillomavirus (HPV) may only need a screening every five to 10 years—and may also be able to start screenings later in life.
These findings, the result of a study published today in the Journal of the National Cancer Institute, are not meant to take the place of current guidelines, say the authors—at least not yet. Rather, they hope the study is a first step toward more research that might eventually spark a policy change.
Many women find the Pap test, the go-to method for cervical cancer screening, uncomfortable and unpleasant. But worse than that, abnormal results can lead to more testing, invasive biopsies, and other treatments that may be unnecessary—or even harmful—to patients, some of whom aren’t in real danger of developing cancer.
And while screenings do catch cancers and save lives, cervical cancer tends to be very slow-growing. “We know that in an average woman, the progression from HPV infection into a cervical pre-cancer—before it even gets into the invasive cancer stage—can take decades,” says Jane Kim, PhD, professor of health decision science at the Harvard T.H. Chan School of Public Health. “This very slow disease process makes Pap smear screenings at these lengthened intervals reasonable.”
That’s especially true for girls and women who’ve been vaccinated against HPV, which causes most cases of cervical cancer. “When you take away the acquisition of HPV, you’re removing a lot of the risk and slowing the process even more,” Kim told Health.
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Since the vaccine only became available in 2006, and because cervical cancer tends to develop very slowly over time, a definitive link between inoculation and reduced cancer incidence has not yet been established. But the research so far as been promising: Earlier this year, studies on women in New Mexico and Alberta, Canada found that the vaccine reduces cervical abnormalities that can lead to cancer.
The new Harvard study used disease-simulation software to estimate the health and economic effects of different screening protocols on women who’d received three different types of currently available HPV vaccines. The goal was to pinpoint strategies that would provide the biggest health benefit in the most cost-effective way.
"This analysis enabled us to examine what would happen if we shifted from the current way we screen for cervical cancer—essentially, recommending the same type of screening for all women—to screening that takes into account whether women have been vaccinated against HPV and therefore face a substantially lower risk of cervical cancer," Kim said in a press release.
According to the simulation, women who received a “nonavalent” HPV vaccine (Gardasil 9) would only need screening four times in their lives—once every 10 years, starting at age 30 or 35. (Current guidelines state that women should get their first Pap test at age 21.) This vaccine, which was introduced in 2014, protects against nine strains of HPV that are known to cause cancer.
Those who got earlier vaccines, Gardasil or Ceravix, would need screenings every five years staring at age 25 or 30. These older versions protect against two strains of HPV—16 and 18—that cause about 70% of cervical cancers.
For vaccinated women, more screenings were not safer. In fact, says Kim, “we found that continuing intensive screening among HPV-vaccinated women yields excessive costs and harms with little to no health benefit.”
The modeling scenario also revealed that screening with HPV testing alone would provide similar health benefits and value as a Pap test or “cotesting,” when both tests are performed at once. Some research suggests that women may one day be able to self-administer HPV tests at home, rather than seeing their doctor, says Kim. But for now, the procedure for HPV and Pap tests is the same, and there’s no difference from a patient’s perspective.
The authors note that their conclusions would only apply to women who received all three doses of an HPV vaccine as pre-teens, as recommended, and have been fully compliant with screening protocols since then. Future studies should take into account real-life scenarios, they say, including women who miss doses, are vaccinated at an older age, or who haven’t stayed up-to-date with their screenings.
And it's too early to recommend that any women forego a scheduled screening or ignore current guidelines, says Kim, since not enough time has passed to show that the HPV vaccine really does what scientists think it does.
“We expect to see that soon,” she says. “And once that happens, and we are convinced once and for all that cervical cancer risk is diminished for these women, I think there will be a bigger impetus to move forward with changes.”
Even if that happens, though, Kim stresses that having fewer screenings shouldn’t necessarily mean having fewer doctor’s visits. “I think we would still want to preserve the opportunity for women, especially as they’re aging, to intersect with their ob-gyn,” she says. “This shouldn’t be conflated with your regular well-woman visit; we’re talking strictly about whether you need this screening or not.”