Several categories of risk factors have been identified that are linked to an increased likelihood of developing lymphoma. Having one or more of these risk factors does not necessarily mean, however, that you will develop lymphoma. Risk factors are merely attributes that have been associated with a statistically greater chance of developing the disease.
Non-Hodgkin lymphoma (NHL) is the fifth most common cancer, while Hodgkin lymphoma is relatively rare. Elderly patients diagnosed with Hodgkin lymphoma tend to have a worse prognosis than younger patients. Although NHL can strike at any age, advanced age is associated with a somewhat greater risk of developing the disease. For instance, people in their early 20s are afflicted with NHL at a rate of about 2.4 cases per 100,000 people. The incidence of the disease climbs to about 46 cases per 100,000 among people in their early 60s. Men are afflicted more often than women, and Caucasians are slightly more likely to develop lymphoma than Asian Americans or African-Americans.
No specific hereditary or genetic link has been identified, but people with a close family member who has been diagnosed with NHL are slightly more likely to be diagnosed with NHL.
Certain infections have been linked to an increased risk of NHL. Most of these cause diseases that affect the immune system. They include human immunodeficiency virus (HIV), Epstein-Barr virus, hepatitis B and C, and Helicobacter pylori infection.
HIV infection, the cause of AIDS, is associated with an increased risk of high-grade lymphomas, including Burkitt lymphoma and diffuse large B-cell lymphoma. The advent of AIDS has been suggested as a possible explanation for the sharp increase in cases of lymphomas since the 1970s. Although cases have nearly doubled since then, advances in diagnosis and treatment have significantly improved prognosis.
Epstein-Barr virus, the cause of mononucleosis (the “kissing disease”), is highly associated with NHLs such as Burkitt lymphoma. Infection with the virus is also linked to an increased risk of Hodgkin lymphoma.
The human herpes virus 8 (HHV8) is capable of infecting lymphocytes, and has been linked to a rare type of lymphoma most commonly found among people who are also infected with HIV.
Hepatitis B and hepatitis C are viruses that attack the liver. Infection with hepatitis C has been linked to a 20 percent to 30 percent increase in the risk of NHL. People infected with hepatitis B are about twice as likely to develop lymphoma as people who have not been infected with the virus.
Helicobacter pylori is a bacterium that lives in the digestive tracts of nearly two-thirds of people around the world. Although a majority of people are evidently unaffected by the bacteria, in some individuals, H. pylori infection causes peptic ulcers. H. pylori is also a risk factor for a type of lymphoma known as gastric mucosa-associated lymphoid tissue lymphoma (MALT).
Compromised Immune System
Any of a number of conditions linked to a compromised immune system may also raise a person’s risk of developing lymphoma. These include: HIV infection, autoimmune diseases, use of drugs and other therapies to suppress the immune system, and hereditary immunodeficiency.
The HIV virus specifically targets the immune system, including lymphocytes called T cells. The emergence and spread of HIV in the early 1980s is believed to account for a near doubling in cases of lymphoma since the 1970s.
Autoimmune diseases occur when the immune system mistakenly attacks the body’s own tissues. Examples include rheumatoid arthritis, systemic lupus erythematous and, type 1 diabetes. Evidence suggests a strong link between some autoimmune diseases and risk of developing lymphoma.
Immune system suppression, primarily used to prevent tissue rejection after organ transplant, is associated with an increased risk of developing lymphoma. Intensive immunosuppressive therapy, with modern immunity suppressing drugs, is a major risk factor for so-called lymphoproliferative disorders, including lymphoma.
Hereditary immunodeficiency affects the viability of the body’s immune system. One of the most dramatic examples is severe combined immunodeficiency (SCID), also known as the “bubble boy” disease, so named for the well-publicized case of a victim who survived for 12 years by living in an isolated, sterile environment. Patients with these disorders are at increased risk of developing lymphoma.
Scientists are presently examining the issue of toxins and lymphoma risk. Exposure to certain toxins—including pesticides, herbicides and environmental carcinogens—have all been linked to an increased risk of lymphoma. Carcinogenic chemicals such as benzene may also increase risk. Certain drugs used to treat other cancers have also been linked to an increased risk of NHL. Ironically, patients who receive chemotherapy to combat Hodgkin lymphoma are at increased risk for subsequently developing NHL.
Radiation is classified as a carcinogen, and radiation exposure has been linked to an increased risk of NHL. Radiation exposure, even from common sources such as diagnostic X-rays, is cumulative. On average, Americans are exposed to seven times more radiation now that they were in the 1980s, primarily due to the growing use (some would argue, overuse) of modern computerized tomography (CT) scanners. A report published in 2007 in the New England Journal of Medicine estimates that CT scans may account for up to 2 percent of new cases of cancer in the United States.