Vaccine could foreshadow the end of cervical cancer
Promising trial results of a vaccine for the virus linked to the
disease has many physicians guardedly optimistic about its use in
prevention.
By
Victoria Stagg Elliott, AMNews staff. Dec. 16, 2002.
Additional information
The news that a vaccine designed to prevent infection with one variant
of the human papillomavirus has some experts contemplating the possible
end of cervical cancer or, at the very least, significant changes to the
traditional approach to women's preventive health.
"If this really comes into play and really eliminates cervical cancer,
we may need to change our recommendations for Pap smear screening," said
Mitchell Edelson, MD, attending surgeon in the gynecologic oncology
department of Fox Chase Cancer Center in Philadelphia. "It could eliminate
Pap smear screening, but that's way down the line."
According to a study published in the Nov. 21 New England Journal of
Medicine, researchers at centers across the United States, led by the
University of Washington in Seattle and funded by Merck Research
Laboratories, randomized more than 2,000 women to receive either three
doses of a vaccine made up of particles derived from HPV-16, the variant
linked to at least half of all cervical cancers, or three doses of a
placebo.
After just more than 17 months, women who received the vaccine were
virus-free. Of those who received the placebo, 41 had acquired the virus,
including nine who had already developed precancerous lesions on the
cervix. The final tallies do not include those who received the vaccine
but tested positive for the virus in the study's first seven months. These
subjects were excluded because researchers believe they acquired HPV
before immunity may have kicked in or before the study began.
"The study is excellent," said F. Ralph Dauterive, MD, chief of
obstetrics and gynecology at the Ochsner Clinic Foundation in Baton Rouge,
La. "The results are very promising."
Researchers intend to follow the women for another two years, and, if
the vaccine proves successful, it has the potential to join the hepatitis
B vaccine as an immunization that prevents cancer. Experts speculate that,
if proven effective in the long run, the HPV vaccine would have an
enormous impact on cervical cancer mortality rates for women without
access to Pap smears.
Nearly half of all cases of cervical cancer are caused by HPV-16.
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"It could have tremendous worldwide implications," said Kelly Molpus,
MD, director of gynecologic oncology at the University of Nebraska Medical
Center in Omaha. "Countries that don't have the facilities for screening
may be more likely to be able to devise some sort of vaccination program
that could prevent potential HPV infection and then hopefully prevent
cervical cancer."
Most American women have access to regular Pap tests which, over the
decades, have led to a significant decrease in cervical cancer mortality
rates. Many doctors, however, say patients would greatly appreciate the
probable reduction in the frequency of the test and the rate of
false-positives that often leads to unnecessary expense, treatment and
anxiety.
"In the short term, where it's going to be important is in decreasing
the number of women who have abnormal Pap smears, especially in this
country, where evaluating women who have abnormal Pap smears is a
billion-dollar industry that causes a lot of anxiety," said Dr. Edelson.
Patients are also more likely to comply with a series of vaccinations
than with years and years of annual screening.
"You should be able to almost eliminate cervical cancer right now, if
people would just go to the doctor and be treated," said Dr. Dauterive.
Remaining questions
Women's health experts generally praised the study, although
researchers and critics alike concede that there are many questions that
still need to be answered.
How long does the vaccine last? What is the ideal dosage and schedule?
Participants in the study did quite well after three doses administered
two months apart. Would one dose be enough? What about two?
There are also concerns about the timing of the vaccine. There is no
evidence that this vaccine would help women who are already infected, and
it could eventually be proven to be important to deliver the vaccine long
before a woman is sexually active and at risk for HPV.
The hepatitis B vaccine has been successfully integrated into the
crowded childhood vaccination schedule, but many physicians question if
parents will be sold on another vaccine that protects their children
against a disease they only have a small chance of developing as adults.
"Most women become HPV infected in adolescence or when they begin
sexual activity," said John Curtin, MD, director of gynecologic oncology
at New York University Medical Center. "If you're talking about
vaccinating kids, the parents are going to have to buy into doing the
vaccination. That's going to be a kind of tough sell. Vaccinating an
entire group of people for a disease that will have a bad outcome in a
very small number, it gets harder and harder to envision its use."
Also, should men be vaccinated? HPV primarily impacts women's health,
and all the subjects in this study were female. However, men can develop
HPV and can infect their partners. In addition, they, too, can develop
related anal and penile cancers, although these are less common than
cervical cancer.
"HPV is a sexually transmitted disease," said Dr. Edelson. "If we're
going to really make strides, we need to prevent infection, not only in
women, but in men."
Many experts also said that to be truly effective, the vaccine would
have to include more variants than just HPV-16. Several multivalent
vaccines are currently being researched.
"We have a lot of unanswered questions, but this was a good step
forward," said Dr. Molpus.
And most importantly: What happens to the Pap smear, the tool that
physicians and patients have trusted for years? "The Pap smear does bring
women in, but so many other things are assessed during that annual exam,"
said Dr. Molpus. "But with education, hopefully we can avoid any
misconceptions."
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ADDITIONAL INFORMATION:
Study shows promise in stopping virus
Objective: Prove the principle that a vaccine made up of
virus-like particles can protect the cervix from infection with the human
papillomavirus and the development of precancerous cells.
Method: More than 2,000 sexually active women were randomized to
receive either three doses of a vaccine designed to create immunity to
HPV-16, the virus variant most commonly linked to cervical cancer, or
three doses of a placebo. They were also screened for the presence of
HPV-16. Subjects found to have the virus during the study's first seven
months were excluded from the analysis.
Results: After nearly 18 months, 41 women in the placebo group
acquired the virus, including nine who developed precancerous lesions on
the cervix. None who received the vaccine did.
Conclusion: The vaccine reduced HPV infection and the incidence of
neoplasia. The vaccine may reduce the incidence of cervical cancer.
Source: New England Journal of Medicine, Nov. 21
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Weblink
Abstract, "A Controlled Trial of a Human Papillomavirus Type 16
Vaccine," New England Journal of Medicine, Nov. 21 (http://content.nejm.org/cgi/content/short/347/21/1645)
Article, "The Beginning of the End for Cervical Cancer?" New
England Journal of Medicine, Nov. 21 (vol. 347, issue 21)
(http://content.nejm.org/cgi/content/full/347/21/1703-a)
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Copyright 2002 American Medical Association. All
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