Blood Transfusions and Prognosis in Colorectal Cancer

Abstract

Busch et al. (May 13 issue)¹ fail to consider the possibility that both autologous and allogeneic blood may contain an immunosuppressive factor that could influence the rate of recurrence of colorectal cancer. Until recently, it was generally thought that the cellular components of transfused blood were responsible for the immunomodulatory effects of transfusion, particularly in renal transplantation. Evidence is accumulating, however, to implicate other components. In colorectal cancer, transfusions of plasma protein fractions and fresh-frozen plasma have been associated with increased tumor recurrence^2,3. Experimental work suggests that humoral rather than cellular components may be more important in transfusion-associated immunosuppression, although this has not yet been shown in tumors in animals. In rats that undergo transfusion, the effects of pretransfusion storage of blood on the synthesis of prostaglandin E₂ by macrophages were greater than the effects due to genetic differences between blood donor and recipient⁴. Serum had the most potent effect, indicating that a major factor activating prostaglandin E₂-mediated immunosuppression in patients who receive transfusions may be humoral. Another study suggested that adenine and some unknown factors in the liquid or plasma portion of stored blood contributed to the inhibition of a normal lymphocytic proliferative response⁵.