Saturday, May 12, 2007

New Evidence Shows Cervical Cancer Vaccine Works

Out ten-gallon hats are off to Dallas/Ft. Worth CBS affiliate 11 TV for this report on an issue that remains "controversial" in the Lone Star State.
(CBS News) The latest clinical trials on the new vaccine that guards against the virus that causes most cases of cervical cancer hold good news for girls and women who've taken it or may take it, and for its manufacturer.

Early Show medical correspondent Dr. Emily Senay explains that Merck's Gardasil is meant to fight off certain strains of human papilloma virus (HPV), which is known to cause cervical cancer.

Though it remains controversial, there's fresh research that Gardasil is effective in fighting off HPV, Senay says, and the news appears to provide even more reason for young girls to be vaccinated, as the federal Centers for Disease Control and Prevention (CDC) and other experts recommend.

HPV is spread through sexual contact, and the strains the vaccine wards off are responsible for about 70 percent of cervical cancer cases, so getting vaccinated can significantly lower a woman or girl's risk of developing the cancer, Senay continues.

Early studies of the vaccine showed it to be so valuable in fighting cervical cancer that the Food and Drug Administration (FDA) gave it fast track approval last June.

Clinical trials continued, Senay points out, to confirm that everything was as it should be, and apparently, it is.

Among previously uninfected patients who received the vaccine, the protection rate after three years was 98 percent, according to results published in the New England Journal of Medicine. So the strains of the virus that account for seven-in-ten cervical cancer cases were effectively stymied.

The CDC recommends vaccination for all girls 11- and 12-years-old. Girls as young as nine are eligible to receive it. Girls and women from age 13 to 26 are also urged to get it, if they still haven't been vaccinated.

The exception to those guidelines involves women who are pregnant. They should wait until after the baby is born to be vaccinated.

The younger a woman or girl is, Senay notes, the greater the chance she isn't already infected with HPV. It's simple probability: The older she is, the more sexual encounters she is likely to have had, and the more opportunities she has had to contract the virus.

Senay stresses that the vaccine does nothing against infections that are already present. Its effectiveness is for patients who are virus-free. So, getting vaccinated while it's still early enough for the vaccine to do some good is important.

The age of the girls involved, and the connection of the vaccine to sexual activity, are contributing to an ongoing controversy over whether states and localities should mandate that they get Gardasil.

Senay also observed that, if a woman is vaccinated before she's sexually active, or at least before she's infected, she still can't be worry-free about getting cervical cancer. Roughly 30 percent of cervical cancers come from strains of HPV that are not diminished by this vaccine. So, no one should let her guard down.

The American Cancer Society recommends cervical cancer screening, including a pap test, within three years of a woman's first intercourse, or by age 21, whichever comes first.

Depending on the kind of pap test used, screening should continue either annually or every-other year.

After age 30, if tests haven't detected a problem, they can be spaced out even more. After age 30, women can also combine their pap tests with a second test that specifically detects the presence of HPV.

The bottom line is to keep getting screened, because there's still a risk of developing the cancer. But all signs point to that risk diminishing sharply, if girls or young women have been vaccinated.

Researchers are not surprised by the new data. Early studies of the cervical cancer vaccine showed it to be so valuable in the prevention of cervical cancer that the Food and Drug Administration (FDA) gave it fast track approval last June.
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1 Comments:

Blogger mhatrw said...

To summarize this published medical journal article:

1. In the FUTURE I trial, GARDASIL demonstrated no clinical efficacy among the general subject population for overall reduction in the rates of grade 2 and grade 3 cervical intraepithelial neoplasia and adenocarcinoma -- the only recognized precursors to cervical cancer.

2. In the larger FUTURE II trial, GARDASIL demonstrated no clinical efficacy among the general subject population for overall reduction in the rates of grade 3 cervical intraepithelial neoplasia and adenocarcinoma -- the strongest (and many would argue only valid) precursors to cervical cancer.

3. Extrapolating from GARDASIL's very limited clinical "success" (in the FUTURE II study only) against grade 2 cervical dysplasias (40% of which regress spontaneously), 129 women would be have to be vaccinated (at a cost of about $60,000) to prevent a single grade 2 cervical dysplasia.

4. GARDASIL's protection against cancer associated HPV strains 16 and 18 appears to cause a disproportionate increase in of pre-cancerous dysplasias associated with other HPV strains associated with cervical cancer "raising the possibility that other oncogenic HPV types eventually filled the biologic niche left behind after the elimination of HPV types 16 and 18."

5. Even if you segregate out the women who hadn't been previously exposed to either HPV 16 or 18, we are talking about just a 17% decrease in all high grade dysplasias (266 out of 6080 vs. 219 out of 6087) -- many of which would spontaneously regress without treatment. So we would have vaccinate 129 women (at about $500 for the three shot regimen) to avoid a single, eminently treatable dysplasia. That's about $60,000 per dysplasia prevented.

This is all directly from the article linked above.

I myself would add that we currently have only 3 years of follow up to go on in terms of both GARDASIL's safety and efficacy among the 16 to 26 year female population, no data concerning its efficacy among 9 to 12 year old girls and only 18 months of follow up on less than 600 total preteen girls in terms of safety data about GARDASIL within its targeted population.

May 13, 2007 1:30 PM  

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