Anal Cancer Incidence, Mortality Rise Sharply in US
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Rates of squamous cell carcinoma of the anus and related mortality have risen sharply over the past 15 years, according to results of a retrospective study published in Journal of the National Cancer Institute.
The findings reflect an urgent need for improved anal cancer awareness and prevention strategies, according to researchers.
“Given the historical perception that anal cancer is rare, it is often neglected,” Ashish A. Deshmukh, PhD, MPH, assistant professor of medicine at UTHealth School of Public Health in Houston, said in a press release. “Our findings of the dramatic rise in incidence among black millennials and white women, rising rates of distant-stage disease, and increases in anal cancer mortality rates are very concerning.”
More than 90% of cases of squamous cell carcinoma of the anus are associated with HPV. Previous studies showed that incidence of this disease more than doubled between the late 1970s and early 2010s in the United States.
Screening for anal cancer has been limited to certain high-risk groups, according to researchers, and the impact of screening on incidence has not been determined.
Deshmukh and colleagues sought to analyze contemporary trends in incidence and mortality of squamous cell carcinoma of the anus in the U.S. They specifically examined trends by stage at diagnosis and year of birth in order to evaluate possible reasons for rising incidence.
Researchers used data from the CDC’s National Program of Cancer Registries and the SEER database to analyze 68,809 patients diagnosed with squamous cell carcinoma of the anus between 2001 and 2015. They obtained mortality data from the National Center for Health Statistics.
Most of the patients (81.8%) were white, whereas 10.2% were non-Hispanic black and 6.6% were Hispanic. Patients aged 50 to 59 years comprised the largest age group (29.8%; n = 20,486), followed by those aged 70 years and older (25.2%; n = 17,331) and those aged 60 to 69 years (24.5%; n = 16,829).
Researchers calculated annual and average annual percentage changes (AAPCs) in incidence and mortality using joinpoint regression, and studied incidence patterns by age group and birth cohort using incidence rate ratios (IRRs) and age-period-cohort modeling.
Results showed incidence of squamous cell carcinoma of the anus increased annually by 2.7% (95% CI, 2.1-3.3) during the study period.
The largest increases in incidence occurred among those aged 50 to 59 years (AAPC = 4.48%; 95% CI, 3.4-5.57) and 60 to 69 years (AAPC = 4.44%; 95% CI, 3.92-4.96).
Overall incidence appeared higher among black vs. white men (AAPC, 2.8% vs. 2.3%) and white vs. black women (AAPC, 3.7% vs. 2.6%). Researchers observed no statistically significant changes among Hispanics and other racial and ethnic groups.
Incidence of distant-stage disease tripled among men (AAPC = 8.6%; 95% CI, 5.4-12) and also rose sharply among women (AAPC = 7.5%; 95% CI, 4.8-10.2). Incidence of regional-stage disease increased equally among both men and women (AAPC, 4.7%).
The AAPC for localized stage was 1.3% (95% CI, 0.6-2) for men and 2.3% (95% CI, 1.8-2.8) for women.
Age-period-cohort modeling showed black men born around 1986 appeared five times more likely to be diagnosed with squamous cell carcinoma of the anus than adults born around 1946 (IRR = 4.7%; 95% CI, 2.1-10.2). White men born after 1960 appeared twice as likely to be diagnosed compared with adults born around 1946 (IRR= 2%; 95% CI, 1.7-2.2), as did white women born after 1960 (IRR = 2.1%; 95% CI, 1.9-2.3).
Anal cancer mortality rates increased 3.1% (95% CI, 2.6-3.5) annually, with increases of 3.4% (95% CI, 2.6-4.2) among men and 2.9% (95% CI, 2.3-3.6) among women.
Mortality rates increased annually by 3.3% for white patients, 3.2% for black patients and 2.5% for Hispanic patients.
Mortality rates increased annually by 3.6% for patients aged 50 to 59 years, 4.9% for patients aged 60 to 69 years and 2.7% for patients aged 70 years and older.
A lack of data on individual risk factors such as HPV, HIV, smoking and organ transplants served as the study’s primary limitation.
Researchers noted that although HPV is preventable through vaccination, half of Americans have not been vaccinated.
“It is concerning that over 75% of U.S. adults do not know that HPV causes this preventable cancer,” Deshmukh said in the release. “Educational campaigns are needed to increase awareness about the rising rates of anal cancer and importance of immunization.”– by John DeRosier
Disclosures: Deshmukh reports an advisory/consultant role with Merck. Please see the study for all other authors’ relevant financial disclosures.
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