How worried should I be about infections that cause cancer?
Guest column by Mikkael A. Sekeres, MD
Infectious agents linked to cancer include bacteria, such as Helicobacter pylori (H. pylori), and viruses, such as human papillomavirus (HPV), Epstein-Barr virus (EBV), and hepatitis B and C. But keep in mind that an exceedingly small percentage of infected people develop cancer.
As an oncologist, when I think about risk factors for developing cancer, I keep in mind a basic principle: Many cancers occur when cells in an organ are encouraged to grow and divide more frequently. Statistically, cells that divide more frequently are more likely to make a mistake, and this mistake can give that cell a growth advantage over other cells, transforming that normal cell to a cancerous cell. Factors such as inflammation or infection cause increased cell turnover or introduce the mistake that drive cells to grow.
Here’s what to know about these infections and how to reduce your risk.
H. pylori
H. pylori can infect the stomach and the duodenum (the first portion of the small intestines) and cause gastritis or peptic ulcer disease. It may pass from person to person through saliva, vomit or stool or through contaminated water or food. Given the ease of H. pylori transmission, it should be no surprise that more than half the population is infected with the bacteria, though only about 30 percent of infected individuals have symptoms.
People with chronic H. pylori infections are at increased risk for gastric cancer or gastric lymphoma; more than 800,000 cancer cases per year are attributed to the infection globally.
The risk of H. pylori infection can be reduced with routine hand-washing and eating food and drinking water from sanitary sources — starting in childhood. Documented H. pylori infections can be treated with a combination of antibiotics and proton pump inhibitors.
HPV
HPV is a common, sexually transmitted infection that can affect the genital area, skin and throat. According to the Centers for Disease Control and Prevention, two decades ago, approximately 14 million new HPV infections occurred annually in the United States. It is estimated the number of certain HPV infections has decreased by more than 70 percent in women age 14 to 24 since then, thanks to the introduction of the HPV vaccine.
Yearly, almost 700,000 cancers worldwide are attributed to HPV, including cancers of the cervix, anus, genital areas, oropharynx, and head and neck. While more than 90 percent of cervical and anal cancers are due to HPV infections, most HPV infections actually resolve spontaneously. The risk of cancer is higher, though, in those with persistent infections. No treatment can eradicate the infection.
The best way to prevent the most common types of HPV is through vaccination, with two doses of the vaccine recommended for children at age 11 or 12, or starting as early as 9 years. While it was a bit uncomfortable for me to think of my three children as future sexual beings at those ages, I nonetheless took all of them to be vaccinated, knowing it would lower their chances of HPV-related cancers as adults. In adults, the vaccine should be considered only for those at risk of infection, such as someone who is previously unvaccinated and has not had sex yet but plans to.
Epstein-Barr virus
Epstein-Barr virus (EBV), the virus responsible for mononucleosis or the “kissing disease,” causes more than 150,000 lymphomas and head and neck cancers globally each year. As the nickname implies, EBV is spread through bodily fluids, most commonly saliva, though most teenagers and young adults will not experience any symptoms when infected. It is estimated that more than 90 percent of the population carries EBV, and while steering clear of people with the infection, good hand hygiene, and avoiding sharing drinks and food can reduce the likelihood of acquiring EBV, infection with the virus is almost inevitable.
The vast majority of people infected with EBV will not develop cancer from the virus. People at higher risk of EBV-related cancers include those who are immunosuppressed following a solid organ transplant (with higher rates in those receiving a transplant of the intestines, lungs, or heart) or bone marrow transplant, or in the setting of infection with HIV.
Hepatitis B and C
Hepatitis B and C infections are the most common causes of liver cancer worldwide, leading to more than 500,000 yearly cases combined. Both viruses can be transmitted through sexual contact, blood or by sharing needles with injection drug use. It is estimated that more than 250 million people are living with hepatitis B worldwide, while 50 million have chronic hepatitis C.
As with HPV, hepatitis B can be prevented through a vaccine series of two or three shots for children and adults 59 years and younger and for older adults with risk factors for hepatitis B. Chronic hepatitis B can be treated with antiviral medications, which are not considered curative.
Unfortunately, there is no vaccine to prevent hepatitis C. The good news, though, is that the development of direct-acting antiviral pills are considered a true medical miracle, in that they cure people with chronic hepatitis C 95 percent of the time, with only an 8-12 week course of therapy. As you might expect, one study of more than 240,000 people with chronic hepatitis C found that treatment with antivirals cut the rate of liver cancer by more than half.
Mikkael A. Sekeres, MD, is the chief of the division of hematology and professor of medicine at the Sylvester Comprehensive Cancer Center, University of Miami. He is author of the books “When Blood Breaks Down: Life Lessons from Leukemia” and “Drugs and the FDA: Safety, Efficacy, and the Public’s Trust.”
