Impact of HIV on Anal Squamous Cell Carcinoma Rates in the United States, 2001-2015

Abstract

Background: Incidence of anal squamous cell carcinoma (SCC) has increased in the United States. People living with HIV (PLWH) have an elevated risk of anal SCC, and changes in the number of anal SCCs among PLWH may have influenced general population trends.

Methods: Data were obtained from a linkage of HIV and cancer registries in 12 US regions. The proportion of anal SCCs occurring among PLWH was estimated by sex, age group, and race and ethnicity. To assess the impact of anal SCCs among PLWH on general population trends, annual percent changes (APCs) in incidence rates including and excluding anal SCCs among PLWH were estimated.

Results: Between 2001 and 2015, 14.5% of 16 110 anal SCC diagnoses occurred in PLWH. In 2013-2015, 35% of anal SCCs among men occurred in PLWH, but only 2% among women. The proportion of anal SCCs among PLWH was highest among 20- to 49-year-olds and Black and Hispanic individuals. General population anal SCC trends among men were strongly influenced by anal SCCs among PLWH: rates increased 4.6%/y (95% confidence interval [CI] = 1.4% to 8.0%) from 2001 to 2009 followed by a statistically non-significant decline (APC = -2.7%/y, 95% CI = -7.1% to 2.0%) from 2009 to 2015, but without anal SCCs among PLWH, rates were stable (APC = 0.7%/y, 95% CI = -0.8% to 2.3%). Anal SCC rates among women increased 3.8%/y (95% CI = 3.2% to 4.4%) during 2001-2012 and then declined statistically non-significantly (APC = -3.8%/y, 95% CI = -6.9% to -0.6%), and anal SCCs among PLWH had little impact on these trends.

Conclusions: During 2001-2015, anal SCCs among PLWH contributed strongly to changes in incidence trends in the general US population among men, but not women.

Figure 1.

Age-adjusted anal squamous cell carcinoma (SCC) incidence (to 2000 standardized population) in the general population including and excluding anal SCCs among PLWH, by age and sex, between 2001 and 2015. The solid lines represent the overall incidence rates of anal SCCs in the general population; the dashed lines represent the incidence rates for anal SCC without anal SCCs among PLWH. A) Incidence rates in men. B) Incidence rates in women. C) Incidence rates in 20- to 49-year-old men. D) Incidence rates in 20- to 49-year-old women. E) Incidence rates in 50- to 79-year-old men. F) Incidence rates in 50- to 79-year-old women.