FDA Approves Gardasil for Prevention of Anal Cancer

A vaccine used to prevent cervical cancer in women recently received FDA approval to include the prevention of anal cancer which struck 5,300 men and women in the United States last year,and led to the death of an estimated 720 people.

Gardasil is a vaccine used for the prevention of human papillomavirus (HPV) types 6, 11, 16 and 18. HPV types 16 and 18 cause an estimated 70 to 75 percent of all cervical cancers, and can also lead to the development of anal, vulvar, vaginal and penile cancer. There are more than 200 types of HPV,most of which show no symptoms, and 30 to 40 of them are transmitted sexually, infecting the anal-genital regions.

According to a report by Gardasil maker Merck,”It is estimated that HPV types 16 and 18 account for approximately 80 percent of anal cancers, 75 percent of cervical cancers, 70 percent of vaginal cancers and 40 to 50 percent of vulvar cancers.” Ninety-percent of all genital wart cases are traced to types 6 and 11.

Gardasil is not a true “cancer vaccine.”Although it does prevent cancer – it only does so by preventing HPV types 6,11,16 and 18, which may or may not lead to cancer.It does not work in patients who already have HPV, or precancerous lesions in the anal and cervical regions. Gardasil is administered as an injection and given three times over a six-month period. After the first injection, the second injection takes place two months later, and the third is given four months after the second injection.

The National Cancer Institute reports that Gardasil is extremely effective at preventing cancers caused by HPV. “FDA-approved Gardasil prevented nearly 100 percent of the precancerous cervical cell changes caused by the types of HPV targeted by the vaccine for up to 4 years after vaccination,” according to an NCI fact sheet. It is thought that Gardasil works longer than four years, but for exactly how long and whether a “booster” shot is needed is still being studied.

With 5,300 cases diagnosed in 2010, anal cancer is less common than cervical cancer which reported more than 12,200 cases diagnosed in 2010. The median age of diagnosis for anal cancer is 60 years old, and the five year survival rate 66 percent. Cancer of the vulva is even more rare than anal cancer with 3,900 cases in 2010, and vaginal and penile cancer are even more rare with 2,300 and 1,300 cases respectively in 2010.

Although Gardasil has been primarily marketed to young women who may be entering sexual activity for the first time, the FDA’s expansion of its role to cover anal cancer means that more men, and homosexual men in particular, may seek out this vaccine. According to the Centers for Disease Control, men who have sex with men are 17 times more likely to develop HPV related anal cancer.

It should be noted that not all cases of anal-genital cancers are related to HPV and sexual activity. Although scientists are not exactly sure of all the causes of these types of cancer, they have identified other risk factors which include: smoking, obesity, poor nutrition, family history, other medical conditions, exposure to certain chemicals and in the case of many vaginal cancers, an old drug called DES (discontinued). It’s also important to note that while Gardasil prevents HPV types 6, 11, 16, and 18, other types of HPV can lead to cancer.

Since Gardasil can prevent HPV related anal-genital cancers (often spread through sexual activity), the logical extension of its application leads one to wonder over its viability toward HPV related oral and neck related cancers. According to that same CDC report on the likelihood of men getting anal cancer, an estimated 5,700 cases of head and neck related cancers diagnosed each year in men are related to HPV. A John Hopkins University study from 2000 shows that 25-percent of 253 people with head and neck tumors were also positive for HPV strain 16.

No clear information on whether Gardasil is in the approval pipeline to cover other types of anal-genital cancer or head and neck cancers was discovered by this writer at the time this article was written. However, with $ 1.1 billion in sales in 2009, one might safely assume Merck is pursuing these avenues of application, prevention and future revenue growth. The FDA approved Gardasil in 2006 for the prevention of genital warts and cervical cancer caused by those 4 types of HPV mentioned above. Gardasil’s patent expires in 2015 and an extension application may give it protection until 2020.

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