Risk factors for non-Hodgkin lymphoma

A risk factor is something that increases the risk of developing cancer. It could be a behaviour, substance or condition. Most cancers are the result of many risk factors. But sometimes non-Hodgkin lymphoma (NHL) develops in people who don’t have any of the risk factors described below.

The risk of developing NHL increases with age. It is more common in people 60 years of age and older. Overall, NHL is more common in men than women, but some specific types of NHL are more common in women.

Some people with certain genetic conditions have a higher than average risk for NHL. Talk to your doctor about your risk. If you have a genetic condition that increases the risk of NHL, you may need to visit your doctor more often to check for NHL. Your doctor will recommend what tests you should have and how often you should have them.

The following are risk factors for NHL. Most of the risk factors are not modifiable. This means that you can’t change them. Until we learn more about these risk factors, there are no specific ways you can reduce your risk.

Risk factors are generally listed in order from most to least important. But in most cases, it is impossible to rank them with absolute certainty.

Weakened immune system

Autoimmune disorders

Certain infections

Previous cancer treatment

Exposure to lindane

Family history of NHL

Breast implants

There is convincing evidence that the following factors increase your risk for NHL.

People who have a weakened immune system have a higher risk of developing NHL. Your immune system can already be damaged when you are born (called congenital immune system damage). It can also be damaged over the course of your life (called acquired immune system damage). No matter when your immune system is damaged, it doesn’t change your risk for developing NHL.

The following can weaken your immune system.

Immunosuppressant drugs affect the immune system so it doesn’t react as it normally would. These drugs are given after an organ transplant so the person’s immune system doesn’t attack the donated organ.

People who take immunosuppressant drugs after a solid organ transplant (such as a kidney, heart or liver transplant) have a higher risk for NHL. People who take these drugs for other conditions, such as rheumatoid arthritis, lupus or inflammatory bowel disease, also have a higher risk of developing NHL. But their risk is lower than for people who take immunosuppressant drugs after an organ transplant.

People with HIV (human immunodeficiency virus) or AIDS (acquired immunodeficiency syndrome) have a greater risk of developing some types of NHL. This risk is decreasing as drugs are developed to treat AIDS and HIV infection.

Immunodeficiency disorders affect the immune system’s natural ability to defend the body against infection. People with immunodeficiency disorders often have frequent infections, which can be severe or unusual. They also have a higher risk of developing certain types of cancer.

You can have an immunodeficiency disorder when you are born. These disorders are usually inherited, which means they are passed from parents to children. Immunodeficiency disorders can also develop over the course of your life. These are called acquired immunodeficiency disorders. They can be caused by another disorder or treatments that suppress the immune system. Inherited immunodeficiency disorders are very rare, but acquired ones are a little more common.

How NHL develops is related to the specific disorder and which part of the immune system it affects. The following immunodeficiency disorders increase the risk of developing NHL.

• ataxia telangiectasia
• Wiskott Aldrich syndrome
• common variable immunodeficiency (CVID)
• severe combined immunodeficiency (SCID)
• x-linked lymphoproliferative disease (XLP)

An autoimmune disorder causes the immune system to attack the body’s own tissue. Some autoimmune disorders have been linked to a higher risk for NHL. But only a small number of NHL cases are linked with autoimmune disorders.

The following autoimmune disorders have been linked with NHL.

• Sjogren’s syndrome
• rheumatoid arthritis
• systemic lupus erythematosus (SLE) (also called lupus)
• celiac disease
• Hashimoto’s thyroiditis

The following viral and bacterial infections can increase the risk of developing NHL. They may damage lymphocytes or constantly stimulate the immune system so it doesn’t work properly.

Epstein-Barr virus (EBV) is a type of herpes virus that causes infectious mononucleosis (also called mono, or the kissing disease). It is linked to Burkitt lymphoma and to NHL in people with a weakened immune system because of HIV/AIDS or immunosuppressant drugs. This virus and Burkitt lymphoma occur most commonly in Africa.

Human T-cell leukemia/lymphoma virus, type 1 (HTLV-1) increases the risk of developing adult T-cell lymphoma and leukemia. It is most common in southern Japan and the Caribbean.

Helicobacter pylori (H. pylori) is a type of bacteria that causes stomach ulcers and inflammation of the stomach lining (called gastritis). It is linked with a type of lymphoma that occurs in the stomach called mucosa-associated lymphoid-tissue (MALT) lymphoma.

Human herpesvirus 8 (HHV-8) is also called Kaposi sarcoma herpes virus (KSHV). It is linked with primary effusion lymphoma, body cavity lymphomas and AIDS-related lymphomas.

Hepatitis C virus (HCV) is a virus that can cause inflammation of the liver (called hepatitis). HCV infection increases the risk of diffuse large B-cell lymphoma (DLBCL), splenic marginal zone lymphoma and lymphoplasmacytic lymphoma.

Campylobacter jejuni (C. jejuni) is a type of bacteria that can cause gastrointestinal (GI) infections. It is linked with mucosa-associated lymphoid-tissue (MALT) lymphoma.

People who have received chemotherapy, with or without radiation therapy, for another type of cancer have a higher risk of developing NHL. This is especially true for people who were treated for Hodgkin lymphoma. But the benefit of being treated for cancer usually far outweighs the risk of developing a second cancer.

The risk of developing NHL is greatest in the first 5 years after treatment. But people who have been treated for cancer have a higher risk of developing NHL for the rest of their lives.

Lindane is a type of insecticide. Lindane is also found in very low doses as a treatment for head lice and mites, but it is only used after other treatments do not work. Studies show that exposure to lindane increases the risk of developing NHL.

People who have a first-degree relative (a parent, brother, sister or child) who has been diagnosed with NHL have a higher risk of developing the disease.

Women with breast implants (silicone and saline) can sometimes develop a rare type of NHL called breast implant–associated anaplastic large cell lymphoma (BIA-ALCL). It starts in the scar tissue that forms around the implant. Recent research suggests that the risk for NHL is higher in women who have textured implants rather than those with smooth surfaces. Health Canada has suspended its medical license for one brand of textured breast implants.

The following factors have been linked with NHL, but there is not enough evidence to show for sure that they are risk factors. More research is needed to clarify the role of these factors for NHL.

• exposure to pesticides
• exposure to trichloroethylene
• occupational exposures (farmers, hair dressers and barbers, welders, and people who work certain industries, such as rubber, printing and forestry)
• hepatitis B virus (HBV) infection
• obesity
• exposure to benzene
• taking tumour necrosis factor inhibitor drugs for autoimmune diseases

To make the decisions that are right for you, ask your healthcare team questions about risks.