Red Blood Cell Transfusion May Increase Risk of Non-Hodgkin Lymphoma, Study Suggests
There is an increased risk of developing non-Hodgkin lymphoma (NHL) after receiving a red blood cell (RBC) transfusion, according to a limited study reported on at the 51st Annual Meeting and Exposition of the American Society of Hematology in New Orleans.
A relationship between RBC transfusions and the subsequent development of NHL has been suggested from previous observational reports. The mechanism is unclear but could be related to the known immunomodulatory effect of blood transfusion. Researchers at Miriam Hospital in Providence, Rhode Island performed a meta-analysis of observational studies to help clarify the strength of such an association, if any.
They searched MEDLINE from January 1966 through June 2009 for observational studies on the association between RBC transfusions and NHL in adults using the keywords “transfusion” and “lymphoma.” Prospective studies and case control studies that reported relative risks (RR), hazard ratios or odds ratios with 95% confidence intervals (CI) were included. A fixed-effect model (FEM) was used to assess the combined outcome of individual studies while a random-effects model (REM) was used, when needed, to account for heterogeneity between studies.
The initial search found 1830 articles. After reviewing the abstracts, 21 papers were selected, from which five prospective and nine case-control studies were included in the final analysis. Based on case-control studies, cases receiving RBC transfusions were associated with a nonsignificant RR of 1.37 (95% CI, 0.94 to 1.87) of developing NHL (P=0.11); a REM was used given the heterogeneity found between studies (I2=90%, Q=90.9, P<0.0001).
Based on prospective studies, those with RBC transfusions had a RR of 1.57 (95% CI, 1.23 to 1.99) of developing NHL (P=0.0003); a REM was used despite finding minimal heterogeneity (I2=34%; Q=7.7, P=0.17). When pooling data from retrospective and prospective studies, RBC transfusions had a RR of 1.43 (95% CI, 1.12 to 1.84; P=0.005); a REM was used given a high degree of heterogeneity (I2=85%; Q=102.0, P<0.0001). No evidence of publication bias was found when pooling all the studies.
The researchers concluded that in both retrospective and prospective studies, there is an increased risk of developing NHL after getting a RBC transfusion. However, the possibility that unndiagnosed NHL was the initial indication for the transfusions was not addressed in the study, limiting the generalization of the conclusions. But since cases were 43% more likely to develop NHL if they had a RBC transfusion, the risk is worth noting. According to the researchers, their findings suggest a conservative approach to RBC transfusions.