By Deena Beasley
LOS ANGELES (Reuters) - U.S. health experts recommended that a test for cancer-causing strains of the human papillomavirus (HPV) be approved to replace Pap smears in screening most women for cervical cancer, but the plan met with some skepticism within the medical community.
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.
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)