Explaining Risk Factors Related to Anal Cancer

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A recent study found rising rates of squamous cell carcinoma of the anus, “particularly advanced-stage disease, and a similar rise in mortality.”1 The authors concluded: “Improved prevention strategies are urgently needed to mitigate the rising [squamous cell carcinoma of the anus] burden among a rapidly growing number of aging U.S. adults.”

A key to prevention is public understanding of the risk factors. As noted in the National Cancer Institute’s Anal Cancer Prevention Physician Data Query, “Being infected with human papillomavirus [HPV] is the main risk factor for squamous cell carcinoma of the anus.”2

“People’s understanding of HPV is somewhat limited, at least from my personal practice,” said Keith Sigel, MD, PhD, MPH, a coauthor of the study and Associate Professor of Medicine, Icahn School of Medicine at Mount Sinai, New York, in an interview with The ASCO Post. “That an infection can cause cancer is not necessarily a natural association to make.”

Health professionals can explain the association, as well as risk factors for HPV and anal cancer, and, for young patients, the importance of HPV vaccination. “[Squamous cell carcinoma of the anus] is preventable through HPV vaccination; however, vaccination coverage (50% in 2017) remains suboptimal in the United States, and less than 30% of vaccine-eligible individuals or their family members received a recommendation for HPV vaccination from their health-care professionals,” the researchers reported.

Safe Sex

Having multiple sexual partners and receptive anal intercourse and being infected with human immunodeficiency virus (HIV) increase the risk of HPV infection and anal cancer. People with healthy immune systems are usually able to clear HPV infections, but “people with HIV are less likely to clear HPV infection, and people with HIV are at a greater than 20-fold increased risk of anal cancer compared to people in the general population,” Dr. Sigel noted.

“We are still really promoting safe sex,” Dr. Sigel said. “There have been some challenges, because now with the availability of pre-exposure prophylaxis, there may be less of an emphasis on using condoms.”


Chronic immunosuppression has also been associated with an increased risk of squamous cell carcinoma of the anus. “Although physicians may be aware that immunosuppression is related to cancer, doctors are potentially not tuned in specifically to anal cancer as a consequence of immunosuppression,” Dr. Sigel said.

“The issue of immunosuppression is really interesting,” Dr. Sigel added. “We couldn’t look at it in the study, but definitely for patients who have had organ transplants, their risk of anal cancer is likely to be similar to people with HIV, and transplant recipients are not a group that is being screened very aggressively,” he noted.

“When they have a choice, physicians would probably prefer not to give people immunosuppressive medications, but many of these situations are unavoidable,” Dr. Sigel acknowledged. “It is important to be aware of the cancer risk, so proper surveillance can be initiated.” ■


1. Deshmukh AA, Suk R, Shiels MS, et al: Recent trends in squamous cell carcinoma of the anus incidence and mortality in the United States, 2001-2015. J Natl Cancer Inst. November 19, 2019 (early release online).

2. Anal cancer prevention (PDQ)—patient version. National Cancer Institute. Updated February 26, 2019.

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