The incidence of anal cancer in the United States has increased since 2001 among people ages 50 years and older, yet declined in younger people, according to research presented at the 2020 annual meeting of the American College of Gastroenterology. This resulted in a 2.1% overall increase in anal cancer incidence. Women are now much more likely to be diagnosed with the disease than men.
“This is a preventable cancer,” said Anas Raed, MD, a gastroenterology fellow at the Medical College of Georgia at Augusta University and lead author of the study. Because more than 90% of cases of anal cancer cases are caused by infection with human papillomavirus, widespread vaccination in childhood against the virus could prevent most cases from occurring, Dr. Raed said. Current CDC recommendations note that children should receive an HPV vaccine at 11 or 12 years of age, or as early as 9 years of age.
Dr. Raed and his colleagues analyzed data from the CDC’s National Program of Cancer Registries and the National Cancer Institute’s Surveillance, Epidemiology, and End Results database. They stratified anal cancer incidence by age, sex and race. They also reported increases or decreases in cancer by histology.
From 2001 to 2016, there were 91,679 cases of anal cancer, of which almost 75,000 occurred in people 50 years or older, according to the researchers. The incidence of squamous cell carcinomas increased by 3.7% in the older population, whereas adenocarcinomas declined by 1.3% in this group. All anal cancers decreased in younger people, and the disease remains relatively rare overall.
Men above age 50 saw a 2.1% increase in incidence in anal cancers of any type from 2001 to 2016, while the incidence declined by 0.6% in men younger than 50. The result was a 1.3% incidence increase overall for men. For women over age 50, the incidence of any form of anal cancer rose by 3.3% during these years, while the incidence declined by 0.2% for those younger than 50. The cumulative increase for women was 2.6%, and women comprised 62.5% of all anal cancer cases.
White patients experienced a 2.2% increase in the incidence of anal cancer over the study period, while Black patients saw a 1.8% increase.
Although procedures like colonoscopy are well developed to detect colorectal cancer before it spreads, in Dr. Raed’s view, clinicians often pay less attention to anal neoplasms. “Don’t forget the anus,” he said.
Joel Palefsky, MD, a professor of medicine at the University of California, San Francisco, regularly treats men living with HIV who have anal cancer. The new findings are “pretty consistent with other data,” Dr. Palefsky said.
Women can acquire HPV by spread from the cervix or through anal sex, Dr. Palefsky noted, which may explain the difference in overall rates of anal cancer between women and men. Men who have sex with men have higher rates of anal cancer than other men, likely due to exposure associated with anal sex.
Whether identification and treatment of a precancerous anal lesion is preferable to early detection of anal cancer without treatment is unclear, as only a small proportion ever progress to anal cancer. Many patients with precancerous lesions may be overtreated, but cancer carries a risk for mortality and a high risk for morbidity, largely due to the side effects of radiation therapy. That risk is reduced with early treatment.
“If I see a precancerous lesion, it’s really hard to do nothing about it,” Dr. Palefsky said. The office-based ablation to remove such lesions is easy for almost all patients to tolerate, to the point that some people return to work the same day, he added.
Still, the empirical effectiveness of treating anal precancers compared with watchful waiting in reducing the risk for cancer remains unknown. Dr. Palefsky is the principal investigator of the ANCHOR study, an ongoing randomized controlled trial of men living with HIV at risk for anal cancer. Half will have their precancerous lesions removed, the others their lesions monitored with no treatment. For more information on the trial, visit anchorstudy.org.
—Marcus A. Banks
This article is from the June 2021 print issue.