Dec. 10, 2003 (New York) -- You can't "catch" cancer like a col
Dec. 10, 2003 (New York) -- You can't "catch" cancer like a cold, but new research now shows that infection with any of a number of different viruses may play an important role in the growth and development of cancer.
More than a dozen different viruses have been linked to various forms of cancer. In most cases, the presence of a particular virus increases the risk of developing cancer or speeds its progression. For example, HIV and other viruses that affect the immune system make infected individuals prone to a variety of cancers by weakening the body's natural defenses.
But in other cases, there is now compelling evidence that certain viruses may also play a critical role in causing cancer. Proving that a particular virus causes cancer, however, is complicated.
"One of the things that is complicated about this is that there is a long time between exposure to the virus and development of the cancer," says Bruce Johnson, MD, of the Dana-Farber Cancer Institute in Boston. "Number two is that it's not a one-to-one thing. There are a lot more people who are exposed [to a virus] than have evidence of a tumor."
Johnson moderated a briefing today in New York City on the virus-cancer link sponsored by the American Society of Clinical Oncology.
Currently, Johnson says the scientific evidence is strongest for the link between cancer and the human papillomavirus (HPV) and the hepatitis B and C viruses, but many other viruses are also under investigation for their ties to cancer.
HPV Linked to More Than Cervical Cancer
HPV has long been associated with an increased risk of cervical cancer, but new research suggests that the virus may also cause head, neck, and anal cancers. HPV is the most common sexually transmitted virus, and about 5.5 million people in the U.S. become infected with HPV each year.
In many people, HPV infection causes no symptoms and resolves on its own without causing illness. But about 18 of the 120 different types of HPV are closely associated with cancer and are known as high-risk types.
"Over the last three years there has been an explosion of data on HPV," says Maura Gillison, MD, PhD, assistant professor of oncology at the Johns Hopkins School of Medicine in Baltimore, who also spoke at the briefing.
Gillison says HPV has now been implicated in 99% of cervical cancer cases. But new studies show that the virus is also responsible for the majority of tonsillar and anal cancers, which helps explain a dramatic rise in these types of cancer in recent years.
Gillison says up to 15% of the cancers reported each year worldwide are caused by HPV infection, and the virus accounts for one-third of all cancers attributable to infectious agents.
