September 26, 2017
Doctor obtaining a cervical smear

Screening for Cervical Cancer

by Berkeley Wellness  |  

Cervical cancer, which is primarily caused by strains of hu­man papillomavirus (HPV), was once one of the most common causes of cancer death in American women. Its symptoms—which include unusual vaginal discharge, abnormal vaginal bleeding, pelvic pain, and pain during intercourse—often go unnoticed because they mimic so many other ailments. Many times cervical cancer has no symptoms—and when symptoms are present, they usually do not appear until the cancer is more advanced.

Beginning in 1955, however, the death rate from cervical cancer declined precipitously in the U.S. The reason: the Pap test, a simple, safe, and painless test developed in the 1940s by George Papanicolaou, M.D., Ph.D., and the most widely used screening tool for any cancer. Cervical cancer develops slowly from precancerous changes called cervical dysplasia. Dr. Papanicolaou discovered that dysplasia and early-stage cancer could be detected on a slide made from a cervical smear. Diagnosed early, before it has spread past the cervix, cervical cancer can be cured over 90 percent of the time.

The Pap test is the most widely used screening tool for any cancer. In Western countries like the U.S. and Canada, where Pap testing is widespread, rates of cervical cancer have plummeted and deaths from cervical cancer are rare (an estimated 4,120 U.S. women died from it in 2016). In poor countries, where most women do not get the Pap test, this cancer remains a major killer.

But might the routine Pap become a thing of the past? In 2014 the FDA approved the first HPV test that can be used as a primary screening test for cervical cancer. Called the Cobas HPV test, it analyzes a sample of cells from the cervix (collected in the same way as for a Pap test) for the presence of any of 14 HPV genotypes that increase the risk of cervical cancer. Before the FDA approval, HPV testing was done only in conjunction with the Pap test, not in place of it.

Nearly all cervical cancers are caused by HPV, with two types responsible for the majority of them. If a woman tests positive for either of these on the HPV test, or has an abnormal Pap smear, it’s recommended that she have an additional test called colposcopy, in which a special magnifying lens is used to directly examine the cervix. If a woman tests positive for any of the 12 other high-risk HPV types, she should have a Pap test, which would then determine if she needs a colposcopy. In either case, a positive HPV test does not mean a woman has cervical cancer, but rather only that she is at elevated risk for it.

Numerous studies have demonstrated that HPV testing is more sensitive than cytology (Pap) testing. One study, published in the American Journal of Clinical Pathology, included more than 47,000 women who had Pap and HPV tests; those who tested positive on either then had biopsies to confirm the accuracy of the tests. It found that the HPV test was better than the Pap test in detecting precancerous cells and reducing the rate of invasive cervical cancer. For example, women with negative HPV results had a lower risk of developing more severe cervical cell changes over the next three years than those with negative Pap results.

Another study, in the Lancet in 2014, combined data from four large trials with more than 176,000 women ages 20 to 64. It similarly concluded that HPV screening leads to better detection of pre-cancer—and thus better protection against cervical cancer itself. A follow-up study done in 2015 found that HPV-based screening provided 60 to 70 percent greater protection against invasive cervical carcinomas compared with Pap testing. An advantage of the HPV test is that the results are fully automated (that is, machine-read); in contrast, the Pap test relies in part on the expertise of medical personnel to detect cell abnormalities.

But the FDA’s decision is controversial. Some public-health and consumer groups oppose the HPV test as a stand-alone screening tool because they think its safety and effectiveness have not been sufficiently tested. Among the concerns are that it could lead to overtesting and overtreatment with more invasive procedures, especially in younger women, who are more likely to test positive for HPV but are at low risk for cervical cancer.

Bottom line: Unlike most cancers, there are excellent screening tests for cervical cancer. What’s most important is to be screened, period, whichever protocol you follow. The guidelines below are reasonable for most women, but talk to your health care provider about which screening option is best for you. The answer may vary by age, personal preference, and other factors.

Screening guidelines

  • Women ages 21 to 29 should have a Pap test every three years.
  • Women under 21 should not be screened for cervical cancer. Women under 30 should not be screened for HPV.
  • Women ages 30 to 65 should have a Pap test every three years or be “co-tested” with an HPV and Pap test every five years. The latter is “preferred” by the American Cancer Society, Americal Society for Clinical Pathology, and the American Society for Colposcopy and Cervical Pathology.
  • Women over 65 should stop routine screening if they’ve had normal results in recent years and are not at increased risk, as should women who have had a hysterectomy with removal of the cervix for reasons other than cancer. Women who have not been adequately screened should have “catch-up” screening after age 65. That includes the 5 percent of American women ages 66 to 70 who haveneverbeen screened for cervical cancer.

Because of improvements in the oversight of laboratories, you can be more confident that a “normal” reading is in fact normal. Every lab now has safeguards against working with a poor sample, and a repeat of the test is requested if a slide is inadequate or can’t be read. Be sure you find out the results of your test: Call the lab or your doctor if no report comes by mail or phone.

Women can also take the following steps to prevent cervical cancer from developing:

Avoid exposure to HPV. About 79 million Americans are currently infected with HPV, according to the CDC, and about 14 million become newly infected each year. Delaying onset of sexual relations, limiting your number of sexual partners, and avoiding sex with people who have had many partners all lower your risk of exposure to HPV. Using condoms also offers some protection, though it is not fullproof.

Do not smoke. An older Swedish study found that smokers infected with cancer-associated strains of HPV were 14 times more likely to develop cervical cancer than infected nonsmokers. The longer they smoked, the higher the risk.

If you use birth control pills, talk to your doctor. Some studies have suggested that long-term use of oral contraceptives (for five years or more) increases the risk of cervical cancer—but only slightly. You and your doctor can decide if the benefits of using birth control pills outweigh this risk.

Also see Racial Gap in Cervical Cancer Deaths.