State Variation in Squamous Cell Carcinoma of the Anus Incidence and Mortality, and Association With HIV/AIDS and Smoking in the United States

Abstract

Purpose: Squamous cell carcinoma of the anus (SCCA) incidence and mortality rates are rising in the United States. Understanding state-level incidence and mortality patterns and associations with smoking and AIDS prevalence (key risk factors) could help unravel disparities and provide etiologic clues.

Methods: Using the US Cancer Statistics and the National Center for Health Statistics data sets, we estimated state-level SCCA incidence and mortality rates. Rate ratios (RRs) were calculated to compare incidence and mortality in 2014-2018 versus 2001-2005. The correlations between SCCA incidence with current smoking (from the Behavioral Risk Factor Surveillance System) and AIDS (from the HIV Surveillance system) prevalence were evaluated using Spearman's rank correlation coefficient.

Results: Nationally, SCCA incidence and mortality rates (per 100,000) increased among men (incidence, 2.29-3.36, mortality, 0.46-0.74) and women (incidence, 3.88-6.30, mortality, 0.65-1.02) age ≥ 50 years, but decreased among men age < 50 years and were stable among similar-aged women. In state-level analysis, a marked increase in incidence (≥ 1.5-fold for men and ≥ two-fold for women) and mortality (≥ two-fold) for persons age ≥ 50 years was largely concentrated in the Midwestern and Southeastern states. State-level SCCA incidence rates in recent years (2014-2018) among men were correlated (r = 0.47, P < .001) with state-level AIDS prevalence patterns. For women, a correlation was observed between state-level SCCA incidence rates and smoking prevalence (r = 0.49, P < .001).

Conclusion: During 2001-2005 to 2014-2018, SCCA incidence and mortality nearly doubled among men and women age ≥ 50 years living in Midwest and Southeast. State variation in AIDS and smoking patterns may explain variation in SCCA incidence. Improved and targeted prevention is needed to combat the rise in SCCA incidence and mitigate magnifying geographic disparities.

FIG 1.

Burden and incidence of SCCA and anal cancer deaths among persons age < 50 years and 50 years and older men and women in the United States in 2001-2005 and 2014-2018: National Program of Cancer Registries and SEER Program and National Center for Health Statistics database. In both men and women, (A) the proportion of SCCA cases and (B) the proportion of anal cancer deaths representative of persons age < 50 and ≥ 50 years increased nationally (2001-2005 and 2014-2018). The incidence and mortality rates^a also increased among persons age ≥ 50 years, but not among persons age < 50 years. ^aRates were calculated as the number of cases per 1,00,000 person-years and age-adjusted to the 2000 US standard population. SCCA, squamous cell carcinoma of the anus.

FIG 2.

Burden and incidence of SCCA and anal cancer deaths according to regions among men and women in the United States in 2001-2005 and 2014-2018: National Program of Cancer Registries and SEER Program and National Center for Health Statistics database. (A) SCCA burden (by region) and (B) anal cancer deaths (by region) among both men and women were highest in the Southeast region, followed by the Midwest region, which collectively contributed to more than 50% of the national burden (2001-2005 and 2014-2018). The incidence rates^a were also high in these regions in recent years, particularly among women. ^aRates were calculated as the number of cases per 1,00,000 person-years and age-adjusted to the 2000 US standard population. For cases diagnosed from 2003 through 2017, 100% of the population is covered for all 50 states and the District of Columbia. In 2001 and 2002, cases that were diagnosed in Mississippi are not available, and in 2018, cases that were diagnosed in Nevada are not available. SCCA, squamous cell carcinoma of the anus.

FIG 3.

State-specific incidence rates and RRs for SCCA among men and women in 2001-2005 and 2014-2018: National Program of Cancer Registries and SEER Program and National Center for Health Statistics database. The incidence rates^a and RRs for each state are highlighted by subregions among men and women: (A) men incidence rate 2001-2005, (B) men incidence rate 2014-2018, (C) men rate ratios, (D) women incidence rate 2001-2005, (E) women incidence rate 2014-2018, and (F) women rate ratios. Among men and women, incidence increased in nearly all states, with prominent increases largely concentrated in the Midwest and Southeast. ^aRates were calculated as the number of cases per 1,00,000 person-years and age-adjusted to the 2000 US standard population. For cases diagnosed from 2003 through 2017, 100% of the population is covered for all 50 states and the District of Columbia. In 2001 and 2002, cases that were diagnosed in Mississippi are not available and in 2018, cases that were diagnosed in Nevada are not available. RR, rate ratio; SCCA, squamous cell carcinoma of the anus.

FIG 4.

State-specific mortality rates^a and RRs for anal cancer in 2001-2005 and 2014-2018: National Center for Health Statistics database; (A) mortality rates 2001-2005, (B) mortality rates 2014-2018, and (C) mortality rate ratios. The mortality rate increased in nearly all states, with a prominent rise concentrated in the Midwest and Southeast. ^aRates were calculated as the number of cases per 1,00,000 person-years and age-adjusted to the 2000 US standard population. RR, rate ratio.

FIG 5.

Correlation between SCCA incidence and AIDS and smoking prevalence: SCCA incidence and AIDS prevalence among (A) men and (B) women and SCCA incidence and smoking prevalence among (C) men and (D) women. There was an association between AIDS prevalence and anal cancer incidence among men and smoking prevalence and anal cancer incidence among women on the basis of Spearman's rank correlation coefficient. Spearman's rank correlation coefficient with corresponding two-sided P values. SCCA, squamous cell carcinoma of the anus.

FIG 6.

Current SCCA screening infrastructure in each state (as of April 2022). The data markers represent locations of high-resolution anoscopy providers. Location details are available in the Data Supplement. SCCA, squamous cell carcinoma of the anus.