Common Virus May be Linked to Colorectal Cancer

But more research needed to prove the connection

FRIDAY, Nov. 15, 2002 (HealthDayNews) -- A virus that lurks harmlessly in the bodies of tens of millions of Americans may play a role in the development of colorectal cancer, new research suggests.

The findings are preliminary, and the germ -- known as human cytomegalovirus -- might not actually contribute to the development of the second deadliest type of cancer, says study co-author Dr. Charles S. Cobbs, a neurosurgeon at the Birmingham VA Medical Center in Alabama.

"But if other people can confirm this data, then the plot thickens," he says.

Colorectal cancer is "notoriously difficult to treat," Cobbs says, especially if it spreads to other organs such as the liver. An estimated 148,300 cases will be diagnosed this year, and the disease will kill approximately 56,600 Americans, according to the American Cancer Society. Among all cancers, only lung cancer takes more lives.

Colorectal cancer typically strikes people over the age of 50. Screening tests are available, and experts estimate that they could detect and prevent 90 percent of the cases.

Cobbs says his investigation into colorectal cancer was inspired by his previous research into the possible role that human cytomegalovirus (CMV) could play in brain tumors.

CMV is a type of herpes virus, a member of the same family of germs that cause cold sores, genital herpes, chicken pox, some kinds of mononucleosis and Epstein-Barr virus.

An estimated 40 percent of the U.S. population has been infected with CMV, says Frank Myers, an epidemiologist with Scripps Mercy Hospital in San Diego. However, except for infants, who can be especially vulnerable, the virus almost never causes symptoms.

"It's thought to lie around latent in the body and not do anything," Cobbs says.

The exceptions are people with weak immune systems, such as AIDS patients, and those who are on special drugs because of organ transplants.

CMV is extremely common in Third World countries, where close to 100 percent of the population may be infected.

The virus is transmitted through saliva and urine, Myers says. Breastfeeding can transmit the disease, says Cobbs, and so can sex. Gay men are especially at high risk.

In his previous research, Cobbs found signs of CMV in almost every brain tumor he examined. Studies from the 1970s suggested that CMV could be linked to other types of cancer, so Cobbs and his colleagues turned to colorectal cancer cells.

The researchers report their findings in tomorrow's issue of The Lancet.

They examined cancerous and normal colorectal cells from 29 people. Signs of CMV infection were found in 80 percent of pre-malignant polyps and 85 percent of cancer cells. "But when we looked at normal cells right next to the tumor cells, none of them were infected" with CMV, Cobbs says.

The meaning of the findings isn't clear, Cobbs adds. CMV "may be completely irrelevant to the cancer process," he says. "Maybe the virus just likes those cells."

However, previous research suggests CMV could pave the way for the development of cancer in the body, he adds.

At this point, there's no reason to make extra efforts to treat more people who are infected with CMV, Cobbs says. Researchers are working on vaccines, though, and some drugs do treat the infection.

What To Do

To learn more about colorectal cancer, visit the Cancer Research Foundation of America or the National Colorectal Cancer Research Alliance.

SOURCES: Charles S. Cobbs, M.D., associate professor, departments of surgery and cell biology, University of Alabama at Birmingham Medical Center, and neurosurgeon, Birmingham VA Medical Center; Frank Myers, CIC, epidemiologist, Scripps Mercy Hospital, San Diego, Calif.; Nov. 16, 2002, The Lancet
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