A large number of studies [26] [27] [28] [29] [30] [31] [32] [33] [34] have also suggested that allogeneic transfusions accelerate cancer growth, perhaps due to altered immune surveillance. These altered immune responses after allogeneic RBC transfusions may also predispose critically ill transfusion recipients to nosocomial infections [35] [36] [37] [38] [39] [40] and increased rates of multiplesystem organ failure [41] , which may ultimately result in higher mortality rates. However, most studies that examined the association between cancer recurrence and postoperative infection after transfusion [42, 43] only provided weak causal inferences because of poor study design and the lack of independence between allogeneic RBC transfusions and the potential complication.