30 August 2011
Vaccines now given to women to prevent cervical cancer appear to also offer strong protection against cancer of the anus.
US researchers studied more than 4200 young Costa Rican women, who were randomly assigned to receive either vaccine against human papilloma virus (HPV) or a hepatitis A vaccine (as a control or comparison).
The HPV vaccine offers protection against HPV types 16 and 18, which are responsible for most cases of cervical cancer and around 80 per cent of anal cancers.
Although anal cancers are rare in the general population, women have twice the incidence compared with men, and overall rates are rising, the researchers said in the journal Lancet Oncology (2011, online 22 Aug).
After 4 years, 62 per cent of the women who received 3 doses of the HPV vaccine showed no sign of HPV infection of the anus, while 77 per cent had no HPV infection of the cervix.
Among those women who had not been previously exposed to HPV, the vaccine prevented anal HPV infection in almost 84 per cent, close to its effectiveness against cervical infection of almost 89 per cent.
"It suggests that in the future, women who receive the preventive HPV vaccines before exposure to the virus will be likely to have less anal cancer," the authors said.
"HPV vaccines have great potential for prevention of a large proportion of HPV-associated cancers ... published evidence exists for vaccine [effectiveness] against HPV 16 and HPV 18 infections at the cervix, vagina, vulva and now anus."
The study also showed the vaccine offered cross-protection against other cancer-causing HPV types 31, 33 and 45 at the anus - the first time this cross-protection has been shown in a non-genital area of the body.
Last Reviewed: 02 September 2011