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 Yes, new research suggests a test for the HPV virus that causes cervical cancer may replace the old-fashioned Pap one day as that cancer's primary screening tool. But even enthusiasts say it will take years of additional research to make such a big switch.
For now, a new trend is the Pap-plus -- both a Pap and an HPV test -- to improve screening accuracy. But government researchers issued a caution this month: Nearly
a 10th of the women over age 30 who get the combo test learn they have HPV even though their Paps show no cancer or even precancerous cells. They'll need repeat checkups, and maybe more in-depth testing, to tease out who's really at risk.
What makes the issue confusing: Women's bodies very often clear an HPV infection on their own, without lasting harm, but it can take a year. The younger the woman, the more likely that HPV is going to be transient.
"One HPV test does not tell you very much. Two consecutive HPV tests are what you need," says Debbie Saslow of the American Cancer Society, who fields phone calls from women frightened by the test mismatch.
"Right now we're, I think, in quite a state of flux," adds Dr. George Sawaya of the University of California, San Francisco, who worries that women aren't being educated enough about the pros and cons of their test options. "We are very thoughtful in telling them how we believe it can add to their care versus how it may be complicating."
Add the still-to-come impact of the new HPV vaccine, and one thing is clear: The days of simple one-size-fits-all advice on cervical cancer screening are ending
-- and women will need to be savvy to realize the newer technology's biggest benefits.
Cervical cancer will strike just over 11,000 U.S. women this year and kill 3,870, the cancer society predicts. Paps are credited for cutting death rates in half since the 1970s, because they can spot precancerous cells in time to remove them and prevent invasive cancer.
HPV, or human papillomavirus, is a common sexually transmitted disease. Some of HPV's dozens of strains can cause cervical cancer if a woman remains infected for a long time
-- more than a year, according to research in this month's Journal of the National Cancer Institute. The HPV test is designed to detect most of the worst strains, using the same cells scraped from the cervix as a Pap does, to signal who's at high or low risk.
Neither test is perfect. Paps can miss cancer signs, which is why women are urged to get them every one to three years. Cervical cancer grows so slowly that an abnormality missed at one checkup can still be caught next time.
Also, roughly 4 million of the nation's 60 million annual Paps appear abnormal but not clearly dangerous. An HPV test that finds no virus gives peace of mind that nothing's wrong, a crucial use of that test.
A positive HPV test detects that virus is present, but can't measure duration of infection or actual abnormalities on the cervix, which require more in-depth follow-up testing.
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"There's absolutely a tradeoff," says Dr. Diane Solomon of the
National Cancer Institute. "There's that balance between wanting to
identify ... young women at risk, but not overtreat."
Yet the HPV test's extra sensitivity, casting a wider net for
who's at risk, is precisely what has researchers around the world
furiously studying it as a potential replacement for the Pap. A list
of studies in the last six months have made headlines by finding a
stand-alone HPV test more accurate than a Pap at identifying women
with cancer or pre-cancer -- almost twice as accurate, in one study.
While that research so far has compared HPV to an older type of
Pap, Canada last month began enrolling 33,000 women into a study to
compare HPV testing to the liquid-based Paps most common today to
see if that makes a difference.
Also, more precise HPV tests, that can pinpoint if women have the
one or two most dire strains, are being developed to offer more
accuracy.
An extra twist: The HPV test may prove especially useful in poor
countries, where cervical cancer still strikes hundreds of thousands
of women who have no access to repeat Paps and might benefit more
from a less frequent viral check.
However all this research turns out, cancer groups for now stand
by their guidelines:
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Women under 30 should get a Pap alone. If it's is inconclusive, HPV testing can rule out who needs further examination. A first test
should be three years after starting sexual intercourse or at age
21.
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Women over 30 have the option of a Pap followed by an HPV test,
or a simultaneous Pap-HPV combo. If both are negative, women can
wait three years to be tested again.
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Women who don't get the HPV test still can wait three years
between Paps, if they've had three consecutive clear Paps.
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Anyone who's received the new HPV vaccine still must follow
guidelines for their age group. That's because the vaccine prevents
some but not all HPV strains, and some teens or young women may have
been infected already before they were vaccinated.
Stay tuned: The advice is almost certain to change in the next
few years.
Paps are "going to be around for the next decade, I will say at
least for the next decade," says NCI's Solomon. "But we may not be
doing as many Paps in 10 years as we're doing now."
[Associated
Press; By LAURAN NEERGAARD]
Lauran Neergaard covers health and medical issues
for The Associated Press in Washington.
Copyright 2008 The Associated
Press. All rights reserved. This material may not be published,
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