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 Roche Holding AG is seeking Food and Drug
Administration approval to market its cobas HPV test, which detects
the DNA of 14 strains of the sexually-transmitted virus, as a
stand-alone tool to screen for cervical cancer risk in women age 25
and older.
But experts said it will be tough to convince doctors to move from
the current testing guidelines, which call for the use of both Pap
tests and HPV tests, since there have been no studies directly
comparing the regimens.
"I think this is a good thing, but the question is it the best
thing," said Dr David Chelmow, who led development of the American
College of Obstetricians and Gynecologists' screening guidelines.
"The preferred method of screening right now is Pap tests and HPV
together. It's not clear which way is better."
Roche presented data on Wednesday showing that with its assay, women
who test positive for HPV 16 or 18, the two most common strains of
the virus, would then undergo a more invasive test known as
colposcopy. Women who test positive for other high-risk HPV strains
would be given Pap tests as initial follow up.
But there are still questions, including how often the test should
be done and the rate of false positives, Dr Chelmow said. "It will
take some time for the ACS (American Cancer Society), the U.S.
Preventive Services Task Force and other big groups to get a chance
to look at the data," he noted. "There is little comparative
effectiveness data comparing primary HPV screening with co-testing."
Current guidelines, set by the American Cancer Society and other
medical associations, call for the dual use of both Paps and HPV
tests every five years to screen for cervical cancer risk in women
between the ages of 30 and 65. For younger women ages 21 to 30, the
recommendations call only for Pap smears every three years.
For decades, Papanicolaou tests, or "Pap smears," have been used to
check for abnormal cells on the cervix as the first line of defense
against cervical cancer. The smears are designed to give direct
evidence of microscopic cancerous changes in cells.
Testing for HPV, which causes more than 99 percent of cervical
cancers, is a relatively new diagnostic tool.
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Vijay Kumar, an analyst at Wall Street research firm ISI Group,
said in a research note that convincing doctors to use the Roche
test as their only tool "will be a huge task, and you will need a
head-to-head trial versus Pap testing before doctors even begin to
be convinced."
He said another barrier to change is the fact that pathologists
make money on Pap tests and referrals, while with HPV tests, the
test provider makes the bulk of the profit.
Pap smears require doctors to scrape the cervix for loose cells to
test, while the HPV test requires them to swab the cervix for a test
sample.
Roche said a large clinical trial of its HPV test found that nearly
1 in 7 women with normal Pap results who were also HPV 16 positive
actually had high-grade cervical disease that was missed.
Each year, about 12,000 women in the United States are diagnosed
with cervical cancer, and around 4,000 women will die from the
disease, according to the Centers for Disease Control and
Prevention.
HPV is also associated with vaginal and vulvar cancer in women and
can lead to penile cancer in men. It may also lead to anal and
throat cancers among men and women as well as genital warts.
(Reporting by Deena Beasley; editing by
Michele Gershberg and Diane Craft)
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