LOS ANGELES - Cases of anal cancer and deaths resulting from the disease are on the rise in the United States, and a new study reveals that older people and young black men are most affected.
Analyzing a span of 15 years, researchers identified about 69,000 cases of anal cancer and 12,000 deaths resulting from anal cancer in the U.S.
Researchers looked at the U.S. Cancer Statistics data set from the Centers for Disease Control and Prevention from 2001-2015 to analyze trends in cases of squamous cell carcinoma of the anus (SSCA), which comprises 80 to 90 percent of all anal cancers diagnosed, as well as trends in mortality rates of SSCA from 2001-2016.
Their findings were published Tuesday in the Journal of the National Cancer Institute.
They found that the number of anal cancer cases increased 2.7 percent per year from 2001 to 2015, while the rate of deaths resulting from anal cancer increased by 3.1 percent per year from 2001 to 2016.
Researchers found that cases of localized stage anal cancer, which is limited to the place where it started, increased about 1.3 percent annually among men and about 2.3 percent annually among women.
When it came to later-stage anal cancer, the increases were more statistically significant. Researchers found that cases of regional stage anal cancer — in which the disease has spread to nearby lymph nodes, tissues or organs — nearly doubled for both sexes. Cases of distant stage anal cancer were found to have tripled from 2001 to 2015.
Cases of anal cancer increased most notably among older adults as well as young black men (born circa 1986).
The increase in older populations might be due to the fact that this age group missed out on the opportunity to receive an HPV vaccine, which was first introduced in 2006 for people ages 9 to 26.
Being infected with the human papillomavirus (HPV) plays a definitive role in the development of anal squamous cell cancer, and evidence of HPV is detected in the majority of anal cancers. HPV is considered to be the most common cause of anal cancers, according to the Mayo Clinic.
Anyone who was over the age of 26 when the first HPV vaccine was introduced in 2006 would have missed out on this preventative measure against anal cancer.
So then why the increase in cases among young black men?
Lead author on the study, Ashish Deshmukh, Ph.D., MPH, who is an assistant professor at UTHealth School of Public Health in Houston, hypothesizes that it has to do with the fact that HIV disproportionately affects young black men. Having HIV is a risk factor for anal cancer.
A 2010 study published in the Journal of Gastrointestinal Oncology pointed to a correlated rise in documented anal cancer cases and the rise of the HIV epidemic — over the course of the 20 years spanning the AIDS epidemic, anal cancer cases quadrupled.
According to this study, the incidence of anal cancer is 40 to 80 fold higher in HIV-positive populations compared to the general population, in part due to the fact that HIV-positive patients are more likely to be co-infected with HPV. In addition, HIV-positive patients suffer from suppressed immune systems, which makes them seven times more likely to have persistent HPV infection.
Deshmukh and his colleagues found another trend that stood out in their recent research — anal cancer cases are on the rise among white women as well.
Deshmukh hypothesized that this may have something to do with changes in sexual behaviors since the sexual revolution of the 1960s. Practices like having an increased number of sexual partners or having receptive anal intercourse, for example, increase the risk of contracting HPV. He said the increase among women may also have to do with the fact that the prevalence of immunosuppression is highest among women.
The study’s authors concluded that the rise in cases of anal cancer, especially advanced stage disease, coupled with the increase in mortality resulting from anal cancer “suggests a true increase in the occurrence of squamous cell carcinoma of the anus.”
They said that improved screening and prevention are necessary to mitigate the rising disease burden.