Q&A: Screening for Cervical Cancer The American Cancer Society recommends that some women over 30 may only need a Pap smear every three years. A look at what's behind the change, and current recommendations on a vaccine that prevents cervical cancer.
NPR logo Q&A: Screening for Cervical Cancer

Q&A: Screening for Cervical Cancer

The Pap smear — a test which looks for the presence of abnormal cells in the cervix — is credited with making cervical cancer relatively rare in the United States. About 10,000 women are diagnosed with the disease each year, compared with the 180,000 women who are diagnosed with breast cancer.

But now, the American Cancer Society is recommending that women over 30 have a genetic test that looks for the virus that causes cervical cancer, the human papillomavirus (HPV). Here, a look at why the recommendation has changed and the issue of HPV vaccination in older women:

Since cervical cancer is now relatively rare in the U.S., why do women need a second test?

Pap smears have played a big role in preventing cervical cancer. About 4,000 women still die from the disease every year, but that is a 70 percent decline in deaths from the mid-20th century. Yet the Pap smear still has its flaws, says Beth Huff, a nurse practitioner at Vanderbilt Medical Center who specializes in cervical issues.

For instance, trying to find precancerous cells with a Pap smear is like searching for a needle in a haystack, she says. "You're looking at 300,000 cells on a slide, and there may only be a handful, five or 10, that are abnormal." The HPV genetic test is considered a far more sensitive test.

How do the tests differ?

For one, Pap smears test for early warning signs of cervical cancer. The HPV test looks for the actual cause of the disease, HPV. The genetic test looks for the DNA of about 13 strains of the virus.

A Pap smear test misses precancerous cells in 25 percent to 50 percent of cases. But combined with the HPV test, a diagnosis is missed in a much smaller number of cases, according to Columbia University pathologist Thomas C. Wright.

Should women ask their doctors for the HPV test?

Women over 30 should ask their doctors for the test, in addition to the Pap smear, says Beth Huff. The risk of new infection is much lower after the age 30 — it drops to 7 percent-10 percent. But if a woman is over 30 and infected, there's a chance she's had the disease for a long time — what's called a persistent infection — and that puts her at a high risk for cervical cancer.

Huff says the American Cancer Society doesn't recommend that younger women ask for the test. For women under 30, the prevalence of HPV is high, but there's also a good chance that their immune systems will take care of the disease. "We would like to save them the anxiety and the cost of testing of a minor infection that will clear up," Huff says.

The American Cancer Society now recommends that if you're over 30, and your Pap smear and HPV test come back negative, you can wait three years, vs. the standard one year, before you have another Pap smear. Why?

If both tests are negative, a woman's risk of developing a significant abnormality within the next three years is extremely low. "Say you go out the night after your Pap smear, and you meet Mr. DNA HPV type 16 — which is one of the high-risk strains," says Huff. "That infection is not going to turn into cancer within a three-year period." If the following Pap smear or HPV test is positive, doctors say that is still an early enough detection to successfully treat the abnormality.

The Centers for Disease Control and Prevention recommends that women under 26 be vaccinated for HPV. Should women over 26 get the vaccine?

"I think there are lots of women over the age of 26 who could benefit from vaccination," says pathologist Thomas Wright, who has consulted with pharmaceutical companies on the vaccine. And some physicians and nurse practitioners are giving the HPV vaccine to women over 26, says Huff. But there are no studies to show what kind of protection the vaccine has in older women. Those studies are underway, says Wright. GlaxoSmithKline is currently testing a cervical cancer vaccine on women up to age 55. The company says it plans to begin filing for FDA approval of the vaccine next month.

If a woman tests positive for HPV, should she still get vaccinated?

Yes, says Huff. Tests can't tell which strain of HPV a woman is infected with. The current vaccine offers protection against the four strains of HPV that cause the majority of disease in women. But only .01 percent of women actually have all four of those strains, says Huff, so the vaccine would offer protection against the strains a woman hasn't been exposed to.

Does insurance cover the HPV test and vaccine?

Most insurance covers the HPV test. But insurance won't cover the vaccine in women over 26, because the FDA has not approved the vaccine for use in older women.