Risk Factors for Non-Hodgkins Lymphoma (NHL)
Although scientists have studied the many cellular changes associated with lymphoma, no one really knows why such changes occur. It is likely that factors increase the risk for non-Hodgkin's lymphoma (NHL). Many factors, such as age and genetics, are non-modifiable (i.e., beyond our control). Other factors, such as environmental or lifestyle-related variables, can be changed (called modifiable risk factors).
It is now known that all cancers, including lymphoma, begin as a mutation (change) in the genetic materialDNA (deoxyribonucleic acid)within certain cells. The external or internal causes of such change probably add up over a lifetime.
DNA errors may occur in the form of translocations, which are damages produced when part of one chromosome becomes displaced and attached to another chromosome. Translocations disrupt the normal sequencing of the genes. As a result, oncogenes (cancer-promoting genes) on the chromosomes may be switched on, whereas tumor suppressors (cancer-preventing genes) may be switched off.
These changes often occur in cases of lymphoma. Physicians test for these translocations to help diagnose the type of lymphoma, determine a patient's prognosis (outcome), and identify cancer recurrence.
Numerous risk factors may be responsible for DNA damage within the body's lymphocytes (specialized white blood cells). The risk factors now believed to have the strongest associations with lymphoma include the following:
Age & NHL
The rate of NHL increases exponentially with age between 20 and 79 years. The rate of HD is highest in two age groups: young adults (aged 1540) and older adults (age 55+).
Gender & NHL
In general, both HD and NHL affect men more often than women.
Infections & NHL
In addition, the risk for developing NHL is increased in people who have been exposed to:
- human T-lymphotrophic virus type I (HTLV-1);
- Epstein-Barr (EBV) virus;
- Helicobacter pylori, a bacteria that may infect the gastrointestinal tract and can cause lymphomas of the stomach;
- human immunodeficiency virus (HIV), the "AIDS" virus; and
- malaria, especially in areas of Africa, where Burkitt's lymphoma is common.
It is important to note that there is no evidence of infection in many HD and NHL patients, so its role in cancer development remains uncertain.
Medical Conditions & NHL
Specific medical conditions may increase the risk for HD or NHL. In particular, HD and NHL are more common among people with a weakened immune system, such as those with the following:
- Autoimmune disease (e.g., HIV/AIDS; disease caused by the body's immunologic attacks against its own tissues)
- Inherited immune deficiency syndromes (e.g., ataxia telangiectasia)
- Organ transplants that require the use of immunosuppressant drugs
Some experts believe that HD is caused by a complex deficiency in cellular immunity. Sucha deficiency may be due to chronic overstimulation by cytokines, which are substances that draw germ-fighting white blood cells to areas of infection.
Chemicals & NHL
Exposure to chemicals also increases the risk for NHL. These chemicals include the following:
- Benzene and certain other solvents,
- Herbicides (weed killers),
- Pesticides (insect killers), or
- Medications (e.g., antiepileptic medicine phenytoin [Dilantin], which can cause reversible overgrowth of lymphoid tissues)
Genetics & NHL
Rates of lymphoma and leukemia (e.g., chronic lymphocytic leukemia [CLL]) are especially high in some Jewish populations, whereas Asian populations rarely develop CLL. Among first-degree relatives (parents, children, siblings) of CLL patients there is a two- to four-fold increased risk for this type of cancer.
Cancer Therapy & NHL
Patients who have received chemotherapy and/or radiotherapy (radiation therapy) for previous cancers have a slightly increased risk for developing NHL or secondary leukemia (leukemia that arises after therapy).