Rates of new anal cancer diagnoses and deaths related to human papillomavirus (HPV), the most common sexually transmitted infection, have increased dramatically over the last 15 years, according to researchers at The University of Texas Health Science Center at Houston (UTHealth). The results of their study, ‘Recent trends in squamous cell carcinoma of the anus incidence and mortality in the United States, 2001-2015’, were published in the November issue of the Journal of the National Cancer Institute.
The study was the first to compare and categorize contemporary national trends in incidence of squamous cell carcinoma of the anus, a type of anal cancer caused by HPV, by stage at diagnosis, year of birth and mortality. It found that anal cancer diagnoses, particularly advanced stage disease, and anal cancer mortality rates had more than doubled for people in their 50s and 60s. The study also revealed that new diagnoses among black men born after the mid-1980s increased five-fold compared to those born in the mid-1940s.
"Given the historical perception that anal cancer is rare, it is often neglected," said Dr Ashish A Deshmukh, the study's lead author and an assistant professor at UTHealth School of Public Health. “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.”
Anal cancer occurs where the gastrointestinal tract ends and is different from colon or rectal cancer due to the cell type and location where cancer develops. Cancer of the anus is most similar to cervical cancer, a cancer of the tissue that lines a woman's cervix. A distant-stage diagnosis means cancer has spread to other parts of the body, decreasing survival rates. Nearly 90% of anal cancers are caused by HPV.
The researchers analysed data from all cancer registries in the US and identified 68,809 cases of anal cancer and 12,111 deaths from 2001 to 2016. They found that anal cancer rates and mortality increased by nearly 3% per year, suggesting it may be one of the most rapidly rising causes of cancer incidence and mortality.
The virus is preventable through vaccination, but 50% of Americans are not vaccinate - setting up a potential wave of future infections leading to cancer. The Centers for Disease Control and Prevention recommends a two-dose regimen for children starting the series before age 15 or a three-dose regimen if the series is started at age 16 through 26.
"The vaccine can also be considered for individuals ages 27 to 45 based on shared decision-making, so it is important that adults speak with their health care providers about getting the vaccine," explained Deshmukh.
"Screening for anal cancer 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," said senior author, Dr Keith Sigel, associate professor of medicine at Icahn School of Medicine at Mount Sinai.
"It is concerning that over 75% of US adults do not know that HPV causes this preventable cancer. Educational campaigns are needed to increase awareness about the rising rates of anal cancer and importance of immunization," added Deshmukh.