A pap smear reveals a group of HPV-infected koilocytes. (Ed Uthman, MD/Wikimedia…)
For generations of women, it's been an ingrained medical ritual: Get a Pap test every year. Now two influential groups of medical experts say that having cervical cancer screening once a year is not necessary and, in fact, should be discouraged.
Many women can wait as long as five years between screenings, the new guidelines say.
The call for screening cutbacks, released Wednesday, is based on evolving knowledge accrued over the last decade about human papillomavirus, a common sexually transmitted disease that causes most cervical cancer, and the availability of an HPV test that shows whether a woman has been infected with the most common variants of the virus.
In recent years, advice on cervical cancer screening has varied widely among medical organizations, with experts recommending screening intervals ranging from one to three years and varying according to a woman's age and whether she is sexually active.
The fact that the two new documents are largely in agreement should reassure women and their doctors that experts have neared a consensus on what has been a controversial issue in prevention medicine, said Debbie Saslow, director of breast and gynecological cancer for the American Cancer Society, which led a consortium that was one of the groups issuing the guidelines.
"I think everyone is on the same page for the first time that I can remember," Saslow said.
By having both a Pap smear and an HPV test — known as co-testing — women ages 30 to 65 can safely go five years between screenings if the results are negative, said Dr. Michael LeFevre, co-vice chair of the U.S. Preventive Services Task Force, which published the other set of guidelines in the Annals of Internal Medicine.
This is the first time that co-testing has been formally recommended as an alternative to Pap smears alone, although some doctors have been offering the tests in tandem for some time.
Studies show that the death rate for cervical cancer is not affected by lengthening screening intervals, LeFevre said, and the move would reduce the number of false-positive tests and unnecessary follow-up procedures.
"You can have fewer Pap smears and it is still as safe and effective," he said. "That is the product of science and what we've learned about HPV."
Both the U.S. Preventive Services Task Force and the consortium of medical groups led by the American Cancer Society continue to emphasize that Pap tests are important, however. More than 11,000 new cases of cervical cancer are diagnosed each year in the U.S. and about 4,000 women die from the disease, largely because they didn't get screened and their cancers were caught too late.
"If you look at cervical cancer today in the U.S., at least half of the women who get it have not been screened," LeFevre said. "Extending out the interval to three years or five years doesn't mean, 'Gee, this must not be important.' "
The new guidelines are the latest in a number of reports issued in recent years by the task force and other medical groups recommending fewer routine cancer screenings because of emerging science showing that test intervals can be safely lengthened and because doing so would reduce the distress caused by false-positives and harm resulting from unnecessary procedures.
In a controversial 2009 decision, for example, the U.S. Preventive Services Task Force recommended scaling back mammogram screening for some women. And in 2010, the American Cancer Society retreated further from recommending routine prostate cancer screening by saying that men over age 50 should discuss the risks and benefits with their doctors before having a prostate-specific antigen test.
In lieu of the combined Pap smear-HPV test combination, the task force screening guidelines also offer women ages 30 to 65 the option of having a Pap smear alone every three years.
The American Cancer Society-led guidelines go slightly further, stating that co-testing is the "preferred" screening strategy for women 30 to 65. Other authors of the document included the American Society for Colposcopy and Cervical Pathology and the American Society for Clinical Pathology; in addition, it was endorsed by the American College of Obstetricians and Gynecologists.
Co-testing is powerful because each exam screens for slightly different things, experts said. The HPV test detects only viral infection that over time can cause cancer in some women. Pap smears, meanwhile, detect precancerous cells that should be treated to prevent cancer.
Until now, use of the HPV test in combination with the Pap smear was not endorsed by the U.S. Preventive Services Task Force, but it changed its position following recent reports that demonstrated the value of using both tests.
One such report, a large study published in December in the journal Lancet Oncology, showed that women who got an HPV test and a Pap smear had fewer cases of precancers and cancers five years later compared with women who got only a Pap smear.
Both sets of new guidelines discourage the use of HPV tests in women under age 30. That's because many in this group have active HPV infections that will soon go away.
"HPV infection is usually self-limited," LeFevre said. "Within a couple of years most women will clear it on their own with no problem."
But since the presence of the virus in women 30 and older may signal a persistent infection that could increase cancer risk, co-testing is of value in women 30 to 65, both documents said.
Both documents recommend several other changes to screening. Young women don't need Pap smears until age 21. Women ages 21 to 29 should be screened with the Pap smear alone every three years. Women can now stop having Pap smears and HPV tests at age 65. Previous guidelines called for halting screening at age 70.
In all, the changes amount to fewer cervical cancer tests for women than ever before, LeFevre noted.
"Most women will view this as a plus," he said.