Anal squamous cell carcinoma incidence rates increased among men and women or among women alone in all countries studied except Asian countries and Spain, according to study results.
The most recent estimates from 2008 indicated there were only 27,000 cases of anal cancer worldwide.
“As anal cancer is a relatively rare cancer, it is often neglected,” Farhad Islami, MD, PhD, strategic director of cancer surveillance research at the American Cancer Society, told HemOnc Today. “We knew that the incidence rates of anal cancer were increasing in some very high–income countries, but we wanted to know about the trends in other countries, especially in economically less developed countries.
“Knowing the trends in incidence of a cancer is important for setting priorities for cancer prevention and care, as well as monitoring progress against cancer,” Islami added.
Islami and colleagues used data from the International Agency for Research on Cancer’s Cancer Incidence in Five Continents series to calculate age-standardized incidence rates for anal squamous cell carcinoma and anal adenocarcinoma for a minimum of 13 years through 2007. Researchers also conducted an extended analysis on data from the United States through 2012.
Results showed anal squamous cell carcinoma incidence rates increased through 2007 among men and women in:
- Australia (men, annual percentage change [APC] after 1983 = 3.3; 95% CI, 2.4-4.3; women, APC after 1997 = 5.9; 95% CI, 3.3-8,7);
- Canada (men, APC after 1983 = 4.5; 95% CI, 2.3-6.7; women, APC after 1983 = 4.9; 95% CI, 3.2-6.6);
- Denmark (men, APC after 1978 = 4.3; 95% CI, 3.2-5.4; women, APC after 1978 = 4.7; 95% CI, 3.8-5.6);
- France (men, APC after 1983 = 2.8; 95% CI, 1.1-4.4; women, APC after 1983 = 1.5; 95% CI, 0.2-2.8);
- Italy (men, APC after 1988 = 5.1; 95% CI, 2.8-7.5; women, APC after 1988 = 5.8; 95% CI, 3.3-8.4);
- The Netherlands (men, APC after 1989 = 6.3; 95% CI, 4.4-8.2; women, APC after 1989 = 6.1; 95% CI, 4.3-7.9);
- the United Kingdom (men, APC after 1979 = 3.3; 95% CI, 2.7-3.8; women, APC after 1979 = 4.5; 95% CI, 3.9-5.1); and
- the United States among black individuals (men, APC after 1975 = 4.2; 95% CI, 2.9-5.4; women, APC after 1975 = 1.4; 95% CI, 0.5-2.4) and white individuals (men, APC after 1975 = 3.3; 95% CI, 2.7-3.8; women, APC after 1996 = 4.6; 95% CI, 2.8-6.4).
Researchers noted the incidence rate was higher among women in these countries except for black men in the United States, who passed the incidence rate of women in 1996.
Anal squamous cell carcinoma incidence increased among only women in Columbia (APC after 1987 = 2.9; 95% CI, .002-5.9), the Russian Federation (APC after 1994 = 10.7; 95% CI, 5.4-16.3), Slovakia (APC after 1980 = 6.5; 95% CI, 3.7-9.5) and Switzerland (APC after 1983 = 2.7; 95% CI, 0.3-5.1).
Rates remained stable over time in India, Israel, Japan, Singapore and Spain.
Data from the extended analysis in the United States showed the increases continued among men and women through 2012.
When researchers evaluated incidence of anal adenocarcinoma, they observed decreasing rates among men and women in The Netherlands; men in Australia, France and Israel; and women in Denmark. Rates increased among men and women in Japan and women in the United Kingdom.
The increasing incidence of anal cancer, especially among women, is likely to be related to a simultaneous increase in HPV infection, Islami said.
“The good news is that HPV infection is preventable by vaccination,” he said. “However, HPV vaccination has not been included in vaccination programs in many countries, or when it has, the uptake is not optimal — including in the United States.”
Safer sexual behaviors can also reduce risk.
“For example, although consistent condom use during intercourse does not provide complete protection, it may reduce the risk for genital HPV infection,” Islami said. “It can also prevent some other sexually transmitted infections and is highly effective in preventing HIV infection.”
Additional data are needed to give a fuller picture of global incidence trends, Islami said.
“We need cancer surveillance data to examine trends in anal cancer in other countries, especially sub-Saharan Africa, where the prevalence of HPV and HIV infection is high in certain populations,” he said. “We could not include any African countries in our analysis due to scarcity of data from population-based cancer registries in Africa.” – by Alexandra Todak
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Disclosure: The researchers report no relevant financial disclosures.