Lymphoma
Lymphoma is a cancer of a part of the immune system called the lymphatic system. There are many types of lymphoma. One type is called Hodgkin's disease. The rest are called non-Hodgkin's lymphoma. Non-Hodgkin's lymphomas begin when a type of white blood cell, called a T cell or B cell, becomes abnormal. The cell divides again and again, making more and more abnormal cells. These abnormal cells can spread to almost any other part of the body. Most of the time, doctors can't determine why a person gets non-Hodgkin's lymphoma. Non-Hodgkin's lymphoma can cause many symptoms, such as
- Swollen, painless lymph nodes in the neck, armpits or groin
- Unexplained weight loss
- Fever
- Soaking night sweats
- Coughing, trouble breathing or chest pain
- Weakness and tiredness that don't go away
- Pain, swelling or a feeling of fullness in the abdomen
Most people with non-Hodgkin lymphoma have no known risk factors, and there is no way to prevent their lymphomas from developing. For now, the only chance for trying to prevent non-Hodgkin lymphoma is by preventing known risk factors such as acquired immune deficiency syndrome (AIDS).
The most preventable cause of immune deficiency is human immunodeficiency virus (HIV) infection. Medical advances have nearly eliminated contaminated blood as a source of HIV infections. HIV is spread among adults mostly through unprotected sex and sharing of contaminated needles by injection drug users. Preventing the spread of HIV would prevent many deaths from infections and from non-Hodgkin lymphoma as well. Treating HIV with 3 or more anti-HIV drugs also seems to lower the chance of developing non-Hodgkin lymphoma very significantly.
Preventing the spread of the human T-cell leukemia/lymphoma virus (HTLV-1) could have a great impact on non-Hodgkin lymphoma prevention in areas of the world where this virus is common, such as Japan and the Caribbean region. The virus is rare in the United States but seems to be increasing in some areas. The same strategies used to prevent HIV spread could also help control HTLV-1.
The recent discovery of the connection between Helicobacter pylori infection and primary gastric lymphomas offers a potential opportunity for prevention, but the benefit of this strategy has not been proven yet. Most people with H. pylori infection have no symptoms, and some have only mild heartburn. Finding the best way to detect and treat this infection in people without symptoms will require more research.
Treatment of cancers with radiation and chemotherapy and the use of immune system-suppressing drugs to avoid rejection of transplanted organs also cause some non-Hodgkin lymphomas. Doctors are studying how to treat cancer and organ transplant patients in ways that do not increase the risk of lymphoma as much. At the present time, however, the life-threatening nature of the diseases requiring these treatments still usually outweighs the small risk of developing non-Hodgkin lymphoma many years later.
What Are the Risk Factors for Non-Hodgkin Lymphoma?
A risk factor is anything that increases your chance of getting a disease such as cancer. Risk factors can be classified as genetic (inherited), lifestyle-related, or environmental. However, most patients with non-Hodgkin lymphoma have no known risk factors. It’s also important to note that having one or more risk factors doesn't mean that you will develop this cancer. Age is the greatest factor for this disease, with most cases occurring in people in their 60s.
Genetic Risk Factors
Several genetic diseases can cause children to be born with an abnormal or deficient immune system. In addition to developing serious infections due to reduced immune defenses, they also have an increased risk of developing non-Hodgkin lymphoma during childhood or as young adults. How this happens is discussed in the section, "Do We Know What Causes Non-Hodgkin Lymphoma?" Although these congenital (present at birth) immune deficiency diseases can be passed on to children, people with non-Hodgkin lymphoma who do not have these inherited diseases do not pass an increased risk of lymphoma to their children.
Lifestyle-Related Risk Factors
Examples of lifestyle-related risk factors for some cancers include exposing skin to strong sunlight, a diet high in fat and low in fruits and vegetables, and habits such as smoking and excessive drinking of alcohol. Lifestyle-related factors such as these do not strongly affect a person's risk of developing non-Hodgkin lymphoma. However, being obese may increase your risk of non-Hodgkin lymphoma.
Environmental Risk Factors
Environmental risk factors are influences in our surroundings, such as radiation, chemicals, and infections.
Radiation: Survivors of atomic bombs and nuclear reactor accidents have an increased risk of developing several types of cancer, including leukemia, thyroid cancer, and non-Hodgkin lymphoma. Patients treated with radiation therapy for some other cancers, such as Hodgkin disease, have a slightly increased risk of developing non-Hodgkin lymphoma later in life. This risk is greater for patients treated with both radiation therapy and chemotherapy.
Chemicals: Some studies have suggested that chemicals such as benzene and certain herbicides and insecticides (weed- and insect-killing substances) are associated with an increased risk of non-Hodgkin lymphoma. Recent studies have found that this is not certain, and research to clarify this issue is still in progress. A recent study from Australia found an increased risk in people who had heavy exposures. Some chemotherapy drugs used to treat other cancers can increase the risk of developing leukemia or non-Hodgkin lymphoma many years later; however, a direct cause and effect relationship has not yet been definitely established. For example, patients who have been treated for Hodgkin disease have an increased risk of later developing non-Hodgkin lymphoma. This may be related to the disease itself or may be an effect of the treatment.
Immune deficiency: Patients with transplanted organs (kidney, heart, liver) and some other conditions like rheumatoid arthritis are treated with drugs that interfere with their immune system to prevent it from attacking the new organs. This effect on the immune system carries a significant risk to the patient of developing non-Hodgkin lymphoma. The exact risk depends on which drugs and at what doses they are used.
Autoimmune disease: In autoimmune diseases, the immune system has become abnormal, and sees the person’s own tissues as foreign, trying to destroy them, as it would a germ. Some autoimmune diseases such as rheumatoid arthritis, lupus erythematosis and others are associated with an increased rate of non-Hodgkin lymphoma.
Infections: Infection with human immunodeficiency virus (HIV), also known as the AIDS virus, is an increasingly common cause of immune system deficiency. HIV infection is a risk factor for developing certain types of non-Hodgkin lymphoma, such as Burkitt lymphoma and diffuse large B-cell lymphoma.
Infection with the human T-cell leukemia/lymphoma virus (HTLV-1) increases a person's risk of developing certain types of T-cell non-Hodgkin lymphoma. This virus is most common in some parts of Japan and in the Caribbean region, but is now found throughout the world. In some isolated areas of Japan, it is responsible for about half of the non-Hodgkin lymphoma cases. In the United States, it causes less than 1% of lymphomas. Like HIV, HTLV-1 spreads through sexual intercourse and contaminated blood and can be passed to children through breast milk from an infected mother..
In areas of Africa where Burkitt lymphoma is common, infection with the parasite that causes malaria and with the Epstein-Barr virus (EBV) as well are important risk factors for this disease. EBV is also associated with lymphomas in developed countries, particularly in patients infected with HIV. EBV is also associated with developing nasal T-cell lymphoma and post-transplant lymphoma.
Credit: National Institute of Health.