Mono Virus Tied to Hodgkin's Disease
Higher lymphoma incidence seen in those with Epstein-Barr bug
WEDNESDAY, Oct. 1, 2003 (HealthDayNews) -- Researchers have found a tantalizing link between a ubiquitous virus and Hodgkin's disease, a type of cancer that affects the body's lymphatic system.
Researchers from Denmark and Sweden disclose in the Oct. 2 issue of the New England Journal of Medicine that Epstein-Barr virus (EBV), the same bug that causes mononucleosis, is associated with an increased risk of certain types of Hodgkin's lymphoma in young adults.
Although all the threads of the tapestry are not yet clear, this does seem to represent a milestone in understanding the possible causes of Hodgkin's.
"It confirms in an important way what we believed about Hodgkin's lymphoma, and that is that as many as one-third or more of the patients have EBV, the causative agent of mononucleosis," says Alan Kinniburgh, vice president of research at the Leukemia & Lymphoma Society. "That's important, because there's a possibility that something that can be done for those patients."
"This is probably one of the largest studies ever done," adds Jay Brooks, chief of hematology and oncology at the Ochsner Clinic Foundation in New Orleans. "We've had hints, but this is the most conclusive."
Scientists have long suspected a link between Hodgkin's and EBV because people who have had infectious mononucleosis also have an increased risk of developing this type of cancer. "It has never before been shown that you have to be infected with EBV prior to the development of Hodgkin's lymphoma," says study author Dr. Mads Melbye, head of the department of epidemiology research at Statens Serum Institute in Copenhagen, Denmark.
This study involved two steps and two groups of patients: One group was composed of 38,555 people who had had symptoms of mononucleosis and whose blood tested positive for EBV, and one group of 24,614 people who had manifested symptoms of mono but no evidence of viral infection in the blood. The second step involved testing biopsy specimens for the presence of the virus in cancer cells.
Overall, 29 tumors were traced to patients who had had mononucleosis. Of those, 16 (55 percent) had evidence of EBV. Those whose cancer cells tested positive for EBV had a fourfold greater risk of developing this type of Hodgkin's lymphoma. Those whose blood tested positive for EBV had a two-to-three times greater risk of developing Hodgkin's disease.
Even so, the authors stress, the chances of developing Hodgkin's even after a bout of mononucleosis is slim: about one in 1,000 versus one in 2,000 for the general population.
According to an accompanying editorial by Dr. Richard Ambinder of Johns Hopkins University, more than 90 percent of adults are infected with EBV and, quite clearly, 90 percent of adults do not develop Hodgkin's. "Most of us will be infected with EBV sometime during our lifetime, but very few of those will get mononucleosis," Melbye points out. Even fewer will develop this cancer.
That leaves several important outstanding questions.
"We're beginning to show from a very large study that there is a relationship between infectious mono and Hodgkin's, but exactly how that occurs we don't know at this point," Brooks says.
Knowing who was susceptible would go a long way towards developing ways to head off the disease. "You can't avoid getting mono, but if we could identify certain individuals who are highly susceptible to tumorogenic activity, then perhaps we could find strategies to prevent the disease in them," Brooks says.
Although scientists haven't answered all the questions, they are that much closer.
"I certainly think this investigation has put us closer to that fact that EBV appears to play a causal role," Melbye says. "It's not the only cause and other factors have to be involved as well, but EBV is involved in the causal pathway of the development of some cases of Hodgkin's, though surely not all of them."