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Gardasil HPV Vaccine Approved for Anal Cancer

On December 22, 2010, the U.S. Food and Drug Administration (FDA) approved the use of Merck's quadrivalent human papillomavirus (HPV) vaccine, Gardasil, for prevention of anal cancer in men and women age 9-26 years. The vaccine -- which targets high-risk HPV types 6, 11, 16, and 18 -- was previously approved for prevention of cervical cancer in young women.

Human papillomavirus, commonly transmitted via sexual activity, causes excessive growth of epithelial cells. Some types (for example 6 and 11) cause genital warts, while others (especially 16 and 18) can cause cervical or anal cancer.

HIV positive people are at greater risk for HPV infection, tend to carry more HPV types, clear infection less easily, and are more likely to develop pre-cancerous cell changes in the genital-anal region caused by the virus. Over time, these changes -- known as cervical or anal intraepithelial neoplasia (CIN or AIN) and squamous intraepithelial lesions (SIL) -- can progress to cancer if not detected and treated.

Invasive cervical cancer is classified as an AIDS-defining condition. Anal cancer, caused by the same high-risk HPV types, has become more common as people with HIV live longer thanks to effective antiretroviral therapy. It is not classified as an AIDS-related condition, but many experts think it should be.

The studies supporting Gardasil's approval for anal cancer prevention were conducted in HIV negative people, but ongoing research indicates that the vaccine is also likely to be effective in HIV positive individuals, and physicians may offer it for this population. Gardasil is most effective when administered to adolescents or young adults, before they acquire HPV via sex.

Below is the text of an FDA press release describing the new indication.

FDA: Gardasil Approved to Prevent Anal Cancer

December 22, 2010 -- The U.S. Food and Drug Administration today approved the vaccine Gardasil for the prevention of anal cancer and associated precancerous lesions due to human papillomavirus (HPV) types 6, 11, 16, and 18 in people ages 9 through 26 years.

Gardasil is already approved for the same age population for the prevention of cervical, vulvar, and vaginal cancer and the associated precancerous lesions caused by HPV types 6, 11, 16, and 18 in females. It is also approved for the prevention of genital warts caused by types 6 and 11 in both males and females.

"Treatment for anal cancer is challenging; the use of Gardasil as a method of prevention is important as it may result in fewer diagnoses and the subsequent surgery, radiation or chemotherapy that individuals need to endure," said Karen Midthun, MD, director of the FDA's Center for Biologics Evaluation and Research.

Although anal cancer is uncommon in the general population, the incidence is increasing. HPV is associated with approximately 90 percent of anal cancer. The American Cancer Society estimates that about 5,300 people are diagnosed with anal cancer each year in the United States, with more women diagnosed than men.

Gardasil's ability to prevent anal cancer and the associated precancerous lesions [anal intraepithelial neoplasia (AIN) grades 1, 2, and 3] caused by anal HPV-16/18 infection was studied in a randomized, controlled trial of men who self-identified as having sex with men (MSM). This population was studied because it has the highest incidence of anal cancer. At the end of the study period, Gardasil was shown to be 78 percent effective in the prevention of HPV 16- and 18-related AIN. Because anal cancer is the same disease in both males and females, the effectiveness data was used to support the indication in females as well.

Gardasil will not prevent the development of anal precancerous lesions associated with HPV infections already present at the time of vaccination. For all of the indications for use approved by the FDA, Gardasil's full potential for benefit is obtained by those who are vaccinated prior to becoming infected with the HPV strains contained in the vaccine.

Individuals recommended for anal cancer screening by their health care provider should not discontinue screening after receiving Gardasil.

As of May 31, 2010, more than 65 million doses of Gardasil had been distributed worldwide, since its approval in 2006 according to the manufacturer, Merck and Co. Inc, of Whitehouse Station, N.J. The most commonly reported adverse events include fainting, pain at the injection site, headache, nausea, and fever. Fainting is common after injections and vaccinations, especially in adolescents. Falls after fainting may sometimes cause serious injuries, such as head injuries. This can be prevented by keeping the vaccinated person seated for up to 15 minutes after vaccination. This observation period is also recommended to watch for severe allergic reactions, which can occur after any immunization.