Red blood cell transfusions raise risk factor for NHL

Findings from a meta-study presented at the American Society of Hematology meeting suggest that receiving a red blood cell transfusion increases one's risk of developing a non-Hodgkin's lymphoma.

Researchers at Brown University Medical School examined data from six prospective and ten case-control studies conducted over the last 16 years and found an increased risk of 1.43 (95% CI 1.12 to 1.84) for NHL among patients with a history of red blood cell transfusions, compared with those reporting never having received such treatments, according to Samir Dalia, MD, of Brown University Medical School in Providence, R.I.

Dalia and his colleagues carried out the meta-study to try and clear up some uncertainty over whether blood transfusions led to an increased risk of NHL since there was evident conflict over this point among the results of the individual studies.

So how is it that a red blood cell transfusion could cause NHL to develop? According to Dalia, there are at least three potential mechanisms;

Viruses. Ones such as Epstein-Barr virus (EBV) are known to cause NHL in immunocompromised patients, and other viruses not yet uncovered could do the same.
Immunosuppression. A red blood cell transfusion causes immunosuppression, which by itself could promote a preexisting NHL to develop.
Other unknown oncogenic factors. Allogeneic transfusions in animal models have led to increased tumor size and promoted metastasis, according to Dalia.

Despite all this, red blood cell transfusions are considered safe and all donations are first screened for pathogens and other contaminants that are known to cause illness and disease.

Source: Dalia S, et al "The association between red blood cell transfusions and development of non-Hodgkin lymphoma" ASH 2009; Abstract 1376. Until published in a peer-reviewed journal, the conclusions from this study are considered preliminary only.