Vaccine approved for anal cancer prevention

, the


that can prevent most cases of cervical


in girls, has won the

as a vaccine to prevent anal cancer, a rare but growing diagnosis in the United States.

The drug agency's approval for Gardasil as an anal cancer vaccine opens the way for the medication's maker, Merck and Co. Inc., to market the vaccine to boys and young men between the ages of nine and 26. The FDA's decision could theoretically double the number of children and young adults urged to take the vaccine. But physicians are most likely to recommend the vaccine first for boys and young men who are gay but have not yet become sexually active and for young men who may engage in sexual relations with other men.

While anal cancer affects both men and women, men who engage in homosexual sex are at greatest risk of contracting anal or genital warts, which can become cancerous over time.

suggested that Gardasil may prevent 78% of anal lesions and anal cancer in men who have sex with men.

Meanwhile, girls starting at age 9 are already

to get the vaccine to block the transmission of four strains of the human papilloma virus (HPV), which collectively account for 75% of cervical cancers, 70% of vaginal cancers and 50% of vulvar cancer cases. The federal government's

is deliberating on a proposal to extend that recommendation to include boys -- both as an indirect means of preventing the transmission of HPV to women and now, as protection for themselves against anal cancer.

Anal cancer is rare, with roughly 5,300 new diagnoses and 720 deaths from the disease each year. Treatment for this cancer typically involves surgery and radiation or


. FDA's Dr. Karen Midthun called treatment for anal cancer "challenging," and said that the use of Gardasil could be "important" in driving down new diagnoses. Most of those

(Twenty million Americans are infected and an additional 6 million yearly are expected to become infected.)