Hodgkin's Disease

Description

Risk Factors

An estimated 7,600 new cases of Hodgkin's disease (HD) were diagnosed in the US in 2003. The incidence has declined significantly over the past two decades at a rate of nearly 1% a year. Experts believe that the malignant process leading to Hodgkin's disease is triggered by a combination of environmental and genetic factors along with a susceptible immune system. The exact triggers, however, are unknown.

Gender and Hormonal Factors

Hodgkin's disease is more common in males than in females. In the last few years, however, the incidence of HD has increased dramatically in young women. Women who get Hodgkin's disease appear to have a slightly lower risk for relapse after treatment than men.

Age

Initial Risk by Age Group. Hodgkin's disease is the most common malignancy in people ages 10 to 30. The average age for developing Hodgkin's is about 28 years old. There are two periods of peak incidence in HD over a lifetime. The major peak occurs in young people between the ages of 15 and 24, with a lesser peak after age 55. The disease can, however, occur at all ages, even in children.

A 2001 Scandinavian study reported an increase in cases among young people. The rate of the disease in older people has declined, however, possibly because better diagnostic procedures are identifying elderly people with non-Hodgkin's lymphomas who would previously have been diagnosed with Hodgkin's.

Prognosis by Age Group. Studies suggest that children with Hodgkin's disease have a better outlook than adults -- particularly elderly adults. One 2000 study suggested, however, that the reason is due to better HD treatments in pediatric medical centers than in adult centers. In support of this, another 2000 study reported that when elderly patients were treated successfully for relapse they did as well as younger people. (In any case, unrelated illness would affect treatment complications and outlook in elderly people.) Some evidence, however, suggests that Hodgkins disease associated with the Epstein-Barr virus is more severe in the elderly (although possibly not in younger people) than other forms of HD.

Epstein-Barr Virus Infection and Infectious Mononucleosis

Young people who have had infectious mononucleosis ("mono"), which is caused by the Epstein-Barr virus (EBV), are at significantly higher risk for Hodgkin's disease. According to a 2003 study, if the malignancy develops in young people who have had mono, it does so on average about four years afterward, with a peak incidence at two and half years. The risk persists, however, for about 20 years after the infection.

EBV most likely plays a role in about half of HD cases. Research suggests that the virus activates some pathway within the lymphocyte cell that leads to cell proliferation.

Only one in 1000 patients with mononucleosis develops Hodgkin's disease, however. It should also be noted that Epstein-Barr virus itself is present in 90% of the population and, in the great majority of these cases, causes a mild infection or none at all, and very few develop HD.Other factors must be present to trigger the malignancy.

EBV appears to be more common in the mixed cellularity subtype of Hodgkin's disease and to occur less often in the nodular sclerosis subtype. In fact, there have been reports of a decline in EBV-associated HD, which coincides with an increasing incidence of nodular sclerosis HD.

Some evidence suggests that ethnic differences may be involved in a lower or higher susceptibility to Hodgkin's disease after an Epstein-Barr infection, with Northern Europeans being at higher risk than other groups.

Family and Ethnic Factors

Hodgkin's disease runs in families in about 5% of cases. Siblings have a threefold higher risk than the general population. Studies suggest, however, that such family clusters are more likely to be due to environmental than genetic factors.

Environmental Toxins

Although high exposure to industrial chemicals has been linked to non-Hodgkin's lymphomas, it is not clear if this is a major risk factor in HD. In a 1999 analysis of studies on the subject, woodworking posed the most consistent risk, although no specific chemical was implicated and not all studies reported a risk. In a 2000 study, automobile workers exposed to cutting oil had a much higher incidence of HD as well as cancers of the lung and testis. Dioxin may also be associated with a higher risk for HD.

Other Factors Associated with Hodgkin's Disease

The following are groups that have a slightly higher than normal risk for HD:

• People who are from small families, have higher educational levels, and are from homes with good hygiene.
• Geographically, people living in developed countries have the highest incidence of Hodgkin's disease. Hodgkin's disease is very uncommon in people who live in Eastern Asia and the Pacific Islands.
• A 2002 study reported a much higher risk for HD in smokers than in non-smokers.
• People who are HIV-positive are at increased risk for Hodgkin's and the incidence is increasing.
• Some studies have reported an association between inflammatory bowel disease (ulcerative colitis or Crohn's disease) and HD. (One study suggested that this relationship may be due to Epstein-Barr virus, which could play causal role in both disorders.)

Crohn's disease, also called regional enteritis, is a chronic inflammation of the intestines which is usually confined to the terminal portion of the small intestine, the ileum. Ulcerative colitis is a similar inflammation of the colon, or large intestine. These and other IBDs (inflammatory bowel disease) have been linked with an increased risk of colorectal cancer.