Risk factors identified for certain lymphoma subtypes

In a large international collaborative analysis of risk factors for non-Hodgkin lymphoma (NHL), scientists were able to quantify risk associated with medical history, lifestyle factors, family history of blood or lymph-borne cancers, and occupation for 11 different NHL subtypes, including less common subtypes. Each year, more than half a million people worldwide are diagnosed with NHL, a diverse group of cancers of the immune system. Although past research suggested different subtypes of NHL may have different causes, those individual studies lacked sufficient statistical power to show this definitively. To overcome this problem, over 100 scientists from the International Lymphoma Epidemiology Consortium pooled data from their studies to produce 13 papers published as a monograph in the Journal of the National Cancer Institute on August 30, 2014.

Analyses from the pooled population included 17,471 people with NHL and 23,096 without the disease. Based on 20 studies conducted in North America, Europe, Israel, and Australia from which the data were pooled, the authors found that:  

• Risks differed significantly among NHL subtypes for medical history factors (autoimmune diseases, hepatitis C virus, eczema, blood transfusion), family history of leukemia and multiple myeloma, alcohol consumption, cigarette smoking, and certain occupations.
• Risks were generally similar among NHL subtypes for family history of NHL overall, recreational sun exposure, hay fever, allergies, and socioeconomic status.
• Autoimmune diseases showed a distinctive pattern: illnesses that activate B-cells were more likely to elevate risk for B-cell lymphomas (e.g., people with a history of Sjögren’s syndrome had nearly 40 times the risk for marginal zone lymphoma). Similarly, those illnesses that activate T-cells were more likely to elevate risk for T-cell NHLs.
• Immune dysfunction was more strongly associated with peripheral T-cell lymphoma, marginal zone lymphoma, Burkitt lymphoma, diffuse large B-cell lymphoma and lymphoplasmacytic lymphoma than it was with mycosis fungoides/Sézary syndrome, chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), follicular lymphoma, and mantle cell lymphoma.

These findings should provide crucial insight into the biological and clinical characteristics that drive NHL subtypes. This large-scale international interdisciplinary effort demonstrates the commitment of the investigators to share data to solve complex problems that require large sample sizes. The effort, which included investigators from the fields of epidemiology, immunology, laboratory science and pathology, was co-led by Lindsay M. Morton, Ph.D., National Cancer Institute’s Division of Cancer Epidemiology and Genetics.