increasing in women or in both men and women in 13 of 18 countries studied,
particularly in the Americas, Northern and Western Europe, and Australia.
The authors say population-based preventive measures, including human
papillomavirus vaccination and advocacy for safe sexual behaviors, may help curb the
surging burden of the disease. The study is published early online in the International
Journal of Epidemiology.
Anal cancer is relatively rare, often-neglected cancer.
The most recent estimates (2008) were that only about 27,000 cases occurred
worldwide (14,500 cases in women and 12 500 in men).
Previous studies have reported a relatively rapid increase in the incidence rate in some
very high-income countries. However, trends elsewhere are largely unknown.
The current study, led by Farhad Islami, M.D., Ph.D., strategic director of cancer
surveillance research at the American Cancer Society, used the latest data using data
from the International Agency for Research on Cancer’s Cancer Incidence in Five
Continents series to estimate anal cancer incidence in 18 countries in four continents
(excluding Africa), including several countries that are economically less developed than
those studied previously.
They found incidence of anal cancer has been increasing—either in both sexes or in
women—in many populations, especially in the Americas, Northern and Western
Europe, and Australia. In those populations, one subtype, anal squamous cell
carcinoma (ASCC) was substantially more common than others, and was the main
contributor to the increase in incidence. Incidence for the other major subtype, anal
adenocarcinoma (AAC) has been stable or decreasing in most populations.
but is likely to reflect changes in prevalence of environmental risk factors,” say the
authors. Those include infection with human papilloma virus (HPV), which is found in
almost all cases of ASCC.
While HPV vaccination can provide protection against anal HPV infection, the authors
note that it is
probably too early to see preventive effects of vaccination of young adults on anal
cancer incidence rates. Also, the vaccine is either not routinely administered or uptake
is suboptimal in countries.
“Certain preventive measures if implemented, including HPV vaccination and
campaigns for safer sexual behaviors, would serve to prevent a substantial number of
anal cancer cases in the future,” the authors conclude.