Examining age-specific trends in the incidence of anorectal cancer associated with human papillomavirus in the United States.

e15690 Background: The incidence of anorectal cancer has increased in the United States. We estimated the potential impact of HPV vaccination on anorectal cancer rates in younger populations. Methods: Data were extracted from the United States Cancer Statistics Public Use Database (USCS), HPV vaccination rates were from the Behavioral Risk Factor Surveillance System (BRFSS), and data on sexual behavior were obtained from National Health and Nutrition Examination Survey (NHANES). Statistical analyses were conducted using the Joinpoint Regression Program (National Cancer Institute) and Pearson correlation coefficients. Results: Based on USCS data, anorectal cancer incidence rates are over 2-fold higher in women compared to men (3.43 vs. 1.57/100,000) in the year 2021. Over the 20 years study period, there has been an average increase of 3.96% per year in women and (p < 0.001) 2.77% annually in men (p = 0.002). After the HPV vaccine's approval for young females in 2006 and young males in 2009, we compared younger versus older individuals lacking access to assess the vaccine's impact on anorectal cancer incidence. Although there is an overall increase in anorectal cancers, the younger cohort 35-39 and 40-44 age groups showed a 1.51% (p = 0.109) and 1.81% (p < 0.001) decrease in incidence from 2001 to 2021. In contrast, the older cohort without access to vaccination, 60-64 and 65-69 years old, observed a 3.72% (p < 0.001) and 3.78% (p < 0.001) increase during this same period, respectively. Using the BRFSS from 2008 to 2021, the rate of HPV vaccination was over 3-fold higher in the younger (19-44 years old) vs. older (45-49 years old) cohort (22.0% vs. 6.92%). Furthermore, data on exposure to HPV vaccination from 2010-2021 showed a negative correlation with anorectal cancer incidence in men (R = -0.749, p-value < 0.005) and women (R = -0.118, p-value = 0.716). Based on gender, among those 35-39 years old, anorectal cancer incidence declined by 2.25% (p = 0.026) in men, with no change in women (AAPC: -0.86, p = 0.170). To analyze the differences in anal sex practices by demographic, we also utilized the NHANES database from 2005-2016 and showed that the proportion of men who have ever practiced anal sex was higher than women (41.2% vs. 37.2% p < 0.001). Conclusions: Compared to men, women have a two-fold higher incidence of anorectal cancer and continues to rise annually possibly due to differences in sexual behaviors. However, in the younger cohort, a significant decrease was observed, possibly associated with HPV vaccination.