WOMEN'S HEALTH
July 13, 2018

A Promising Alternative to the Pap Smear

Testing for the human papillomavirus, or HPV, catches cervical cancer sooner than Pap smears do. But there are other risks to consider.

Women may soon have a more sensitive test for cervical cancer than the Pap test used by most gynecologists. In a four-year Canadian study, women who had a negative human papillomavirus, or HPV, test had fewer than half as many late-stage cervical cancers four years later, compared to women whose liquid-based cytology test, today's most common variation of the Pap, was negative.

The HPV test caught more cancers at an early stage, when they are easier to treat.

The Pap test has been around a long time and is familiar to most women. It tests for cervical cancer by looking for abnormal cells under the microscope.

The HPV test, on the other hand, searches for DNA or RNA that indicate an infection with the human papillomavirus. This virus is the cause of 99.7 percent of all cervical cancers, though not all infections with it lead to cancer. It has only been available since 2014.

The study compared Pap testing to HPV testing in over 19,000 Canadian women.

The HPV test is better at detecting cervical cancers earlier, when they are easier to treat. It does, however, lead to more false positives than the Pap.

The women were split into two groups. Half underwent a liquid-based cytology (LBC) Pap test and a follow-up LBC test 24 months later if the first was negative. The other half had an HPV test. At 48 months, four years after the study's start, all women returned for both a cytology — Pap — test and an HPV test.

The main focus was on the number of grade 3 or worse cervical cancers found in each group at the 48-month exit testing. Grade 3 cervical cancers are those which have spread from the cervix to the lower part of the vagina or to the walls of the pelvis.

Only 2.3 cancers that were grade 3 or worse were found per thousand women in the HPV group, while more than twice as many were seen in the cytology group. Similar results were reported for grade 2 cancers, which were nearly twice as prevalent in the LBC group.

These results indicate that the HPV test is better at detecting cervical cancers earlier, when they are easier to treat, among women in this age group. It does, however, lead to more false positives than the cytology testing of a Pap smear. Since the HPV test accurately shows an infection, it may mean that for some women with no cancer present, their doctor may still suggest further medical procedures, such as a colposcopy (magnified examination of the cervix) and sometimes a biopsy, procedures that carry their own risks .

Are the extra cancers that the HPV test catches worth the unnecessary procedures that some women without cancer will have to undergo? That's something you might want to discuss with your doctor.

Current recommendations by the American Cancer Society (ACS) for women between the ages of 30 and 65 call for a Pap test combined with an HPV test every five years. The ACS also considers getting a Pap test every three years a reasonable option.

As L. Stewart Massad, of the Department of Obstetrics and Gynecology, Washington University School of Medicine, says in his editorial on the study, “Fortunately for women, both modalities are so effective for cancer screening....In the near future, however, the declining prevalence of HPV disease following HPV vaccination will make the marginally better sensitivity of co-testing irrelevant.”

The study, and the accompanying editorial, can be found in JAMA.

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