Anal cancer diagnoses in men in the United States aged 50 and over rose over a decade and states with a higher frequency of AIDS diagnoses tended to have a higher frequency of anal cancer diagnoses too, a national study of anal cancer mortality published in the Journal of Clinical Oncology reports.
The study authors suggest that structural inequalities leading to late HIV diagnosis, poor access to care and a diagnosis of AIDS contribute to a higher risk of anal cancer in some parts of the United States for men.
In women, anal cancer rates were strongly correlated with smoking prevalence but not with AIDS. Alarmingly, anal cancer in women aged 50 and over had become almost as common as cervical cancer in some states in the midwest and south-east of the United States by 2014-2018.
The study results are in contrast to a recently published study from the Netherlands, showing that anal cancer diagnoses in gay and bisexual men living with HIV have declined since 2013 and that screening was associated with better survival after a diagnosis of anal cancer. Dutch HIV clinics began to screen gay and bisexual men with HIV for precancerous anal lesions in 2007 although screening is not universal.
Almost all anal cancers are caused by human papillomavirus (HPV). Vaccination against the cancer-causing strains of HPV is highly effective in preventing cervical and anal cancer. Anal cancer has become the most common non-AIDS-defining cancer in people with HIV and there is evidence that HIV-related immunosuppression increases the risk of developing anal cancer. Along with age, smoking is a major risk factor for anal cancer.
Researchers at some of the largest cancer clinics in the United States, led by Dr Ashish Deshmukh of the Medical University of South Carolina, investigated the factors associated with anal cancer in the United States, focussing on AIDS and smoking.
The researchers used the US Cancer Statistics and National Center for Health Statistics datasets to estimate state-level incidence of anal cancer and deaths from anal cancer. They compared two periods (2001-2005 and 2014-2018) and looked at correlations between anal cancer and current smoking behaviour and with state-level AIDS incidence. It was necessary to use AIDS incidence rather than HIV diagnoses because reporting requirements for HIV diagnosis vary between US states.
Between 2001 and 2018, there were 88,159 cases of anal cancer diagnosed in the United States and 14,483 people died of anal cancer.
The incidence of anal cancer increased in the period 2014-2018 compared to 2001-2005 by 46% overall and by 63% in people aged 50 and over. The annual incidence was 3.3 cases per 100,000 people in men aged 50 and over in 2014-2018 and 6.3 cases per 100,000 in women aged 50 and over in the same period.
Irrespective of age, the greatest increase in incidence occurred in the midwest and south-eastern states, where anal cancer diagnoses in women increased by 62% and 50% respectively. In men, incidence almost doubled in Tennessee and Iowa, increased by approximately two-thirds in Kentucky and Louisiana and by approximately 50% in Delaware, Wisconsin, Alabama, Indiana and Michigan. In women, incidence doubled in Mississippi, North Dakota, Nebraska, West Virginia and increased by between 78% and 90% in Minnesota, Iowa, Tennessee and Wisconsin.
The increase in incidence in the Midwest and South-Eastern states was even more pronounced in men and women aged 50 and over.
But in men under 50, anal cancer incidence declined significantly in the US as a whole and at state level, it declined substantially in California, New Jersey, Florida, Illinois and Colorado. In the period 2015-2018, anal cancer incidence fell by 21% per year in California. Incidence also fell significantly in women under 50 in California.
Deaths due to anal cancer approximately doubled in eight states in the Midwest and South-Eastern regions.
Smoking rates at state level were strongly correlated with anal cancer incidence in women aged 50 and under (r=0.74, p< 0.001).
Anal cancer incidence was correlated with AIDS prevalence in men (r=0.47, p<0.01) but not in women. The study authors suggest that barriers to HIV care leading to late HIV diagnosis and a higher incidence of AIDS may explain the increased incidence of anal cancer, especially in young men in southern states.
They say that a focus on screening for anal cancer in people with HIV is unlikely to have an impact on the incidence of anal cancer in women, among whom smoking is the more substantial risk factor.
They also express concern that states with the highest incidence of anal cancer have some of the lowest rates of human papillomavirus vaccination and high levels of HPV vaccine hesitancy among parents of adolescents. They say aggressive efforts are need to improve HPV vaccination rates and reduce geographical disparities in the United States.
In an accompanying editorial, Dr Alexandra Hotca and Dr Karyn Goodman, cancer specialists at Icahn School of Medicine, New York, say that not enough people at high risk of anal cancer are being screened, that guidelines for screening are lacking and that infrastructure for screening is often absent outside urban areas. They say that clinics that can carry out high-resolution anoscopy and treatment of precancerous lesions need to be established in regions where anal cancer prevalence is rising.
The lack of screening facilities is a serious challenge. Nationally, the study identified 181 clinics that provide high-resolution anoscopy screening. Almost half (47%) are in five states (California, New York, Florida, Maryland and Massachusetts). Poorly served states include Tennessee and Indiana (one site each) and Pennsylvania (three sites). Alabama, Alaska, Arkansas, Mississippi, Iowa, Kansas, Nebraska, North and South Dakota and all the Mountain states except Colorado and Utah lack screening sites.
Damgacioglu H et al. State variation in squamous cell carcinoma of the anus incidence and mortality, and association with HIV/AIDS and smoking in the United States. Journal of Clinical Oncology, published online 28 November 2023.
Hotca A, Goodman KA. Trends in anal cancer: leveraging public health efforts to improve cancer care. Journal of Clinical Oncology, published online 12 January 2023.