Racial and ethnic differences in human papillomavirus (HPV)-associated anal cancer

A55 Introduction: Racial and ethnic differences in the incidence and stage distribution of anal cancer have not been well described previously. Approximately 90% of anal cancers are attributable to human papillomavirus (HPV), of which 92% are due to HPV types 16 and/or 18. Methods: Population-based cancer registry data from 38 states and Washington D.C., collected with support from the Center for Disease Control and Prevention’s National Program of Cancer Registries and the National Cancer Institute’s Surveillance, Epidemiology, and End Results program, were analyzed using SEER*Stat. Anal cancers diagnosed in 1998-2003, with microscopically confirmed histological types known to be associated with HPV (85% of all anal cancers), were included in the analysis: squamous cell, transitional cell, basaloid, and cloacogenic carcinomas. Incidence rates and stage distributions were age-adjusted to the 2000 U.S. standard population and were calculated by sex, race, and ethnicity. Race and ethnicity were not mutually exclusive. Results: For 1998-2003, the average-annual incidence rate of HPV-associated anal cancer was 1.28 per 100,000 persons [95% confidence interval (CI) 1.26-1.30]. Whites had the highest (1.31 per 100,000; 95% CI 1.29-1.33), and Asian/Pacific Islanders had the lowest (0.33 per 100,000; 95% CI 0.28-0.39) incidence of anal cancer. The incidence of anal cancer was significantly higher among black men [rate ratio (RR) 1.21; p≤0.05] compared to white men. In contrast, the incidence was significantly lower among black women (RR 0.81; p ≤ 0.05) compared to white women. The incidence of anal cancer among Asian/Pacific Islanders was significantly lower than whites for both men (RR 0.20; p ≤ 0.05) and women (RR 0.28, p ≤ 0.05). The incidence of anal cancer was significantly lower among Hispanic men (RR 0.76, p ≤ 0.05) compared to non-Hispanic men. The incidence rate among Hispanic women was not statistically significantly different from non-Hispanic women. The majority of cases of anal cancer were diagnosed at in situ or localized stage (58.1%). Asian/Pacific Islanders were more often initially diagnosed with regional or distant stage disease (27.5% and 11.8%, respectively) than blacks (23.5% and 7.3%, respectively), and whites (22.2% and 6.6%, respectively). Among Hispanics, 21.5% were diagnosed with regional disease (vs. 22.3% of non-Hispanics) and 7.5% were diagnosed with distant stage disease (vs. 6.6 % of non-Hispanics). Conclusions: A significant proportion of all anal cancers are theoretically preventable with the HPV vaccine. Blacks had the highest incidence of HPV-associated anal cancer among men, while whites had the highest incidence among women. A higher proportion of Asian/Pacific Islanders were diagnosed with regional or distant stage disease, compared to whites and blacks. Continued public health surveillance is needed to determine the impact of the HPV vaccine on different racial and ethnic populations. Because the quadrivalent HPV vaccine is only approved for use in women, further research on the potential use of the HPV vaccine in men is also warranted.