Gardasil - the Cervical Cancer Vaccine?

 
Posted on Wednesday, April 18, 2007
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FDA Approval Not Based On Actual Cancer Prevention

The FDA-approved cervical cancer vaccine "Gardasil," has been debated for a number of reasons including its cost of $360 (plus the cost of doctors visits to get the shots) and the fact that it is approved for young girls and the moral and sexual implications associated with this. Up until recently, however, no one challenged the vaccine on the grounds of its presumed safety and efficacy. The fact that it is FDA approved was considered prima facie evidence that the vaccine is both safe and effective. We must remember, however, that the FDA that approved Gardasil is an agency with countless conflicts of interest that has approved drugs and vaccines that were later found to be dangerous or deadly such as Vioxx and RotaShield.

When Cancer Monthly began looking at the research that enabled this "cervical cancer vaccine" to receive FDA approval we were astounded to find that this approval was not based on the vaccine's actual prevention of cervical cancer. Instead a surrogate was used - precancerous lesions. We were pleased to see a recent article in the Wall Street Journal (WSJ) that echoed these same issues - "Questions on Efficacy Cloud a Cancer Vaccine" April 16, 2007; Page A1. The WSJ stated, "The Food and Drug Administration didn't ask its panel of experts advising on Gardasil to rule on whether the vaccine specifically prevented the cancer itself."

Cancer Not Measured

How effective is Gardasil in decreasing the incidence of cervical cancer? 100%? 50%? No one really knows because this question has not yet been answered. As of today, the Gardasil vaccine has never been proven to decrease the actual incidence of cervical cancer. In the studies that led to the vaccine's approval, the incidence of cervical cancer was not measured. Instead CIN (cervical intraepithelial neoplasia) 2/3 and AIS (adenocarcinoma in situ) were used as the surrogate markers for prevention of cervical cancer because according to the vaccine's insert "CIN 2/3 and AIS are the immediate and necessary precursors of squamous cell carcinoma and adenocarcinoma of the cervix, respectively." While this is true it is also true that CIN 2/3 and AIS usually do not lead to cancer. For example, according to published data, CIN2 only leads to invasive carcinoma 5% of the time and CIN3 only leads to invasive carcinoma 12% of the time.1

HPV Alone Insufficient to Cause Cancer

In addition, Gardasil is targeted against Human Papilloma Virus (HPV) (types 6, 11, 16, and 18). However, during discussions at the FDA it was admitted that HPV alone is insufficient to cause cancer. Dr. Elizabeth Unger of the Centers for Disease Control stated, "So it is believed that infection alone is insufficient to cause cancer, and additional factors are required for neoplasia. There are certainly lots of questions about HPV infection…"2 This point is echoed in the medical text book Cancer: Principles & Practice of Oncology whose editors include Dr. Vincent DeVita, Jr. who was President of the National Cancer Institute and Dr. Steven Rosenberg, Chief of Surgery at the National Cancer Institute. According to this text, "HPV infection is not sufficient for cervical carcinogenesis…"3

HPV the Correct Target?

This is of course quite rational. If HPV alone caused cervical cancer than the number of cases in the U.S. would be the same as the number of women with HPV infections. Since only a relatively small percentage of HPV infected women get cervical cancer this raises the question whether a vaccine against HPV is the right target at all? In fact, according to the text Cancer: Principles & Practice of Oncology, "In most studies, HPV status was not a strong independent prognosticator of outcome in cervical cancer patients; however there appears to be a trend for HPV-negative tumors to do worse …those tumors containing HPV DNA tend to be of an early stage and low grade."4 This suggests that if the goal is to reduce deaths from cervical cancer the target should not be HPV at all because the tumors without HPV actually "do worse."

Concern at the FDA

Obviously a vaccine designed to prevent cervical cancer should have measured cervical cancer during testing, but it did not. During meetings at the FDA, Dr. Karen Goldenthal of the FDA discussed this very point. She said, "Now, here is some advantages of cervical cancer as an endpoint. Clearly the major concern is cervical cancer. This would be viewed as very, very definitive data, and it may be easier to identify any unanticipated vaccine associated problems."5 Nonetheless, the FDA did not require that the actual number of cervical cancers be measured. As a result we now have an FDA approved "cervical cancer vaccine" that is yet unproven to reduce or prevent cervical cancer.

Leap of Faith

As quoted in the Wall Street Journal article, Scott Emerson, a professor of biostatistics at the University of Washington who sat on the FDA advisory committee, says he's not persuaded the vaccine is worth the billions of dollars likely to be spent on it in coming years. "I do believe that Gardasil protects against HPV 16 and 18, but the effect it will have on cervical-cancer rates in this country is another question entirely…There is a leap of faith involved," Dr. Emerson said.

End Notes

(1) Arends MJ, et al., Aetiology, pathogenesis, and pathology of cervical neoplasia. J Clin Pathol. 1998 Feb;51(2):96-103. Available here: http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=500501&blobtype=pdf
(2) Dr. Beth Unger. See Minutes from: FDAVaccines and Related Biological Products Advisory Committee, November 28, 2001, p. 21 available here: http://www.fda.gov/ohrms/dockets/ac/cber01.htm#Vaccines%20&%20Related%20Biological
(3) Vincent T. Devita, Jr., et al., editors, Cancer Principles & Practice of Oncology, 6th edition, volume2, p. 1523
(4) Vincent T. Devita, Jr., et al., editors, Cancer Principles & Practice of Oncology, 6th edition, volume2, p. 1523
(5) Dr. Karen Goldenthal. See Minutes from: FDAVaccines and Related Biological Products Advisory Committee, November 28, 2001, p. 83 available here: http://www.fda.gov/ohrms/dockets/ac/cber01.htm#Vaccines%20&%20Related%20Biological