Since the start of the new millennium, the incidence of anal cancer cases and the number of deaths due to the disease have risen dramatically in the United States, with older individuals more likely to be diagnosed with advanced disease, according to results from a large-scale registry study.
The study was published online by the Journal of the National Cancer Institute on November 19.
Ashish A. Deshmukh, PhD, MPH, from Center for Health Services Research, UTHealth School of Public Health, Houston, Texas, and colleagues set out to examine trends in incidence (2001–2015) and mortality (2001–2016) for squamous cell carcinoma of the anus (SCCA).
They found that the incidence of cases of SCCA, more than 90% of which are associated with human papillomavirus (HPV), had risen by almost 3% per year, a figure matched by the annual increase in mortality rates.
The team also found that anal cancer diagnoses (particularly of advanced-stage disease) and anal cancer mortality rates had more than doubled for people in their 50s and 60s.
In addition, new diagnoses among black men born after the mid-1980s increased fivefold compared to those born in the mid-1940s.
"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," Deshmukh commented in a statement.
He added that it is also "concerning" that recent research by the same team showed that 75% of US adults "do not know that HPV causes this preventable cancer."
Deshmukh believes that "educational campaigns are needed to increase awareness about the rising rates of anal cancer and importance of immunization," which can be considered for individuals aged 45 years and younger.
Senior author Keith Sigel, MD, PhD, MPH, associate professor of medicine at Icahn School of Medicine at Mount Sinai, New York City, raised the idea of screening for anal cancer.
He said that it is "not currently performed except in certain high-risk groups, and the results of this study suggest that evaluation of broader screening efforts should be considered."
Details of the Findings
Previous studies have indicated that the incidence of SCCA more than doubled between the late 1970s and the early 2010s. The authors note that during that period, large shifts occurred regarding the risk factors for the disease, which were linked to changes in sexual behaviors and the HIV epidemic.
However, they point out that it is not clear whether the observed increases are due to improvements in diagnostics, which may have led to an increase in the identification of early-stage tumors, or reflect a true increase, which would be seen across tumor stages.
To investigate further, the researchers trawled the Centers for Disease Control and Prevention's National Program of Cancer Registries US Cancer Statistics dataset and the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) Program for cases of SCCA.
Death certificates obtained from the National Center for Health Statistics were examined to identify deaths from anal cancer. Cases were then linked to cases in the SEER Program to identify cancer characteristics at diagnosis.
The team identified 69,809 cases of SCCA over the study period (2001–2015). The majority of cases occurred in women (64.9%) aged 50 years or older (79.5%) and non-Hispanic whites (81.8%). A few more than half (50.3%) had localized-stage disease.
The overall incidence of SCCA increased by 2.7% per year from 2001 to 2015. The annual increase was 2.2% in men and 3.1% in women.
Among black men, the increase in incidence was slightly higher than among white men, at an average annual percentage change of 2.8% vs 2.3%.
Among women, the pattern was reversed; the annual increase was 2.6% in black women and 3.7% in white women.
The investigators also found an increase in incidence among younger Americans. In comparison with individuals born in 1946, among black men born around 1986, the incidence rate ratio of SCCA was 4.7, whereas for white men and white women born around 1960, the incidence rate ratios were 2.0 and 2.1, respectively.
From 2001 to 2016, there were 12,111 deaths from anal cancer. Overall mortality rates increased by 3.1% per year, at 3.4% per annum among men and 2.9% in women.
Mortality rates increased significantly for individuals aged 60 to 69 years, at an average annual percentage change of 4.9%.
Discussing the findings, the authors suggest that the increase in anal cancer mortality in older individuals is likely linked to the increase in rates of advanced-stage SCCA in people aged 50 years or older.
This, in turn, "may reflect an increasing prevalence of immunosuppressed adults in the US." One hypothesis is that "comorbid and iatrogenic immunosuppression may have their largest impact in the elderly, impairing both HPV clearance and immunologic cancer surveillance."
The research was supported by the National Cancer Institute of the National Institutes of Health and the intramural research program of the National Cancer Institute. Deshmukh received a consulting fee from Merck on unrelated projects. Coauthor Joel M. Palefsky reports relationships with several pharmaceutical companies. The other coauthors have disclosed no relevant financial relationships.
J Natl Cancer Inst. Published online November 19, 2019. Abstract
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