|
HomeTopics...Hodgkins DiseaseHodgkins Causes
The Causes of Hodgkin's Disease: Genetic and Viral LinksDespite the fact that Hodgkin's disease has been researched more than any other type of lymphoma, a single cause for the disease has yet to be established. Several risk factors, however, have been identified, including infection by the Epstein-Barr virus, the presence of Reed-Sternberg (RS) cells, general immune system impairment, exposure to environmental carcinogens and a family history of Hodgkin's disease.
Infection with the Epstein-Barr Virus
Several studies have concluded that exposure to the Epstein-Barr virus (EBV) may trigger the onset of HD. For instance, people who have had infectious mononucleosis, an infection caused by the Epstein-Barr virus, have been shown to be at greater risk of developing HD.
According to Dr. Nancy Mendenhall of the Department of Radiation Oncology, University of Florida, "HD seems to spread from one lymph node group to another, consistent with an infection from an agent such as EBV that would cause an upper respiratory infection." Dr. Andrew Grulich, National Centre for HIV Epidemiology and Clinical Research (NCHECR), University of New South Wales, Sydney, Australia, has also found that infection with the Epstein-Barr virus may trigger HD. Research conducted at the NCHECR found that the EBV is present in as many as fifty percent of all cases of HD. One theory is that the Epstein-Barr virus reduces the immune response of the killer T-cells that, in a healthy individual, would eradicate the Reed-Sternberg cells and prevent them from multiplying. Other studies have suggested that EBV may even cause a mutation in the p53 gene, a gene that helps the body fight cancer. The mutation of this gene enhances the cancer cell's capacity to grow relentlessly. Further research is required to confirm these theories.
Age GroupOccurrences of Hodgkin's disease decrease in middle age, but increase again from the age of fifty."
 Although Hodgkin's disease can occur at any age, it is rarely found in childhood and early adolescence. Only ten to fifteen percent of cases occur in children under sixteen years of age. Strangely, following a peak in early adulthood, the occurrence of the disease decreases throughout middle age, only to increase again after age fifty.Statistics show that Hodgkin's disease is far more prevalent in two specific age groups:
Researchers speculate that the initial peak in early adulthood may result from genetic inheritance or hormonal causes, particularly given the male predominance of this group. In the older group of patients the risk of HD applies to both sexes and increases with age.
A Defective Immune SystemRecent research has established a definite link between immune system malfunction and the occurrence of HD. For example, a number of studies of people with HIV and AIDS who have poorly functioning immune systems show that they are ten times more likely than the general population to develop Hodgkin's disease.
Dr. Andrew Grulich contends, "In people with HIV, the risk of HD appears to increase as immune function declines."
Use of Immunosuppressive DrugsCertain drugs, especially immunosuppressive drugs used in conjunction with organ transplants, have been shown to increase the likelihood of developing Hodgkin's disease. Drugs used for the treatment of rheumatoid arthritis are also suspect.
Genetic Causes of Hodgkin's DiseaseScientific opinions differ regarding a link between genetics and the likelihood of developing HD.
One study of twins (Mack, et al, 1995) identified a significant genetic susceptibility to HD in young adulthood. They studied 366 sets of twins in which one of the twins had been diagnosed with Hodgkin's. In the fraternal twins (twins from two separate eggs) none of the 187 unaffected twins developed HD. In the identical twins (derived from the same fertilized egg, and therefore having the same genetic composition), ten out of the 179 unaffected twins developed HD. Other experts believe a genetic cause for HD is unlikely. For instance, Dr. Alan C. Aisenberg, Department of Hematology and Oncology, Massachusetts General Hospital, argues that HD is no more likely to be hereditary than other types of cancer. He contends that the four- to five-fold increase of HD among identical twins is more likely due to environmental than genetic factors.
Environmental FactorsExposure to carcinogens, particularly in the workplace, may increase the risk of developing HD. Other environmental pollutants such as pesticides, herbicides and various viruses have also been linked to an increased occurrence of the disease.
Long-Term PrognosisAlthough Hodgkin's disease was responsible for the death of approximately 1,320 people in the United States during 2004, death rates from the disease have fallen by more than sixty percent in recent years.
The main cause of death during the first fifteen years following treatment is a recurrence of Hodgkin's disease. After fifteen to twenty years, death is more likely to be due to other factors, such as a different type of cancer.
Five-Year Prognosis: Cause for OptimismThe five-year relative survival rate is a standard international statistical benchmark used to define the percentage of cancer patients who survive at least five years following diagnosis. The five-year relative survival rates do not include patients who die of unrelated diseases. This five-year standard is merely a statistical tool used for establishing survival rates, and many patients survive much longer than five years.
Today, thanks to clinical trial research, advances in treatment, and availability of refined diagnostic procedures, the prognosis for HD patients has improved considerably. The overall five-year survival rate is currently 84 percent. When this overall survival rate of 84 percent is analyzed in greater detail, an interesting picture emerges:
Today's statistics refer to people diagnosed with Hodgkin's disease at least five years ago. More recently diagnosed patients are at a major advantage, due to the many new treatments that have been tracked for only a few years.
Resources
1Up Health (2002). Hodgkin's lymphoma causes, incidence, and risk factors. American Cancer Society (updated 2005). What is Hodgkin's disease? American Cancer Society (updated 2005). What are the key statistics for Hodgkin's disease? Benzene AML Leukemia Lawsuits (nd). Hodgkin's disease & lymphoma related to benzene exposure. Beers, M. H., & Berkow, R. (ed). Hodgkin's disease. The Merck Manual of Diagnosis and Therapy, 17th Edition. Merck Research Laboratories, NJ, 1999. CancerBacup (nd). Understanding Hodgkin's disease. Cossman, J., Annuinziata, C. M., Barash, S., Staudt, L., Dillon, P., He, W., Ruccuardu-Castagnoli, P., et al. (1999). Hodgkin's disease genome-wide genome expression. Blood, 1999, 94(2), 411-416. Fauci, A., Braunwald, E., Isselbacher, K., Wilson, J., Martin, J., Kasper, D., Hauser, S., & Longo, D. (ed). Harrison's Principles of Internal Medicine, 14th Edition. McGraw-Hill, NY, 1998. Lymphoma Information Network (2000). Childhood Hodgkin's disease. Lymphoma Research Foundation (2002). Learn about lymphoma. Mack, M. T., Cozen, D. O., Shibata, D. K., Weiss, L. M., Nathwani, B. N., Hernandez, A. M., Taylor, C. R., et al. (1995, February 16). Concordance for Hodgkin's disease in identical twins suggesting genetic susceptibility to the young-adult form of the disease. New England Journal of Medicine, 332, 413-419. National Cancer Institute (updated 2002). What you need to know about Hodgkin's disease. Oncology Channel (updated 2005). Hodgkin's disease. Patten, E. (2000). Hodgkin's disease is curable despite unknown origin. CBS Health Watch, 2000.
|
|
