By Diana Swift

The incidence of anal cancer (AC), grew in the U.S. from 2001 to 2016, particularly in women ages 50 and up, researchers reported.

An analysis of a national database showed that the anal cancer incidence rate rose steadily, with an annual percent change (APC) of 2.1 (95% CI 1.7-2.5) overall, and an APC of 2.8 (95% 2.5-3.1), in those ages ≥50, according to Anas Raed, MD, of Augusta University in Georgia, and colleagues.

Of 91,679 AC cases reported during 2001 to 2016, 81.3% occurred in individuals ages ≥50, with the great majority (82.5%) being squamous cell carcinoma (SCC), they said in a presentation at the American College of Gastroenterology virtual meeting.

Raed and colleagues also reported that females had a higher risk than males at APC 3.3 (95% CI 3.0-3.6) versus 2.1 (95% CI 1.6-2.5), while Caucasians had a higher risk than Blacks at APC 3.0 (95% CI 2.7-3.4) versus 2.1 (95% CI 1.6-2.5).

Anal cancer is an uncommon, but preventable disease, with 8,590 new cases projected (5,900 in women; 2,690 in men) and approximately 1,350 disease-related deaths (810 in women; 540 in men) for 2020. More than 90% of cases are linked with human papilloma virus (HPV), and anal cancer rates, especially for SCC, have been rising in most other developed countries in recent decades.

Raed called for widespread preventive, screening, and surveillance strategies to reverse this trend, and reduce demographic disparities in this preventable neoplasm. "There is definitely some stigma attached to this cancer, so some people may be more reluctant to come forward when they experience symptoms," said Raed. "It's important that during colonoscopy physicians examine the anal area for abnormal lesions."

The authors used data from the Surveillance, Epidemiology, and End Results to "Assess the [APC] of anal cancer among the U.S. population younger and older than 50" and to "Explore the APC among these two populations by histology type, gender, and race," they stated. Anal cancer cases were identified using the site from the ICD code for Oncology, coded as "anus." By demographics, 62.5% of the cases were in women, 86.7% in Caucasians, 10.9% were in African Americans, and 2.4% were in others.

Individuals ages ≥50 had an increased incidence of SCC with an APC 3.7 (95% CI 3.3-4.0), whereas adenocarcinoma incidence decreased during this period with an APC -1.3 (95% -1.9 to -0.7).

The APC was the greatest in the age group 55-59 at 4.3 (95% CI 3.6-5.0), they stated. Among younger individuals (ages <50), the 45-49 age group showed an upward trend in anal cancer (APC 1.0, 95% CI -0.4 to 2.5).

Raed noted that the faster rise in Caucasians was puzzling because this group would seem to have greater access to healthcare and immunization. Also, reasons for the increasing rate in women remains unclear.

"I am concerned about the rising incidence, but do not have a ready explanation for the racial and gender disparity," commented J. Michael Berry-Lawhorn, MD, of the University of California San Francisco.

Berry-Lawhorn, who was not involved in the current study, is participating in the nationwide randomized ANCHOR study to determine whether treating the precancerous lesion known as HSIL (high-grade squamous intraepithelial lesion) could prevent the development of anal cancer.

"Prevention also requires a group of providers trained in high-resolution anoscopy," said Berry-Lawhorn. "Until we show definitively that we can prevent cancer, there has been limited interest in screening the general population, but there may be ways of identifying particularly high-risk women who could be targeted but who currently are not."

Raed emphasized that the key to eradication is HPV vaccination. "It's alarming to know that more than 50% of U.S. adults are not vaccinated against HPV," he said. "Therefore, it's imperative that patients be educated and encouraged to discuss HPV vaccination with their primary care physicians."