Update on granulocyte transfusions: accumulation of promising data, but still lack of decisive evidence

Inconsistent results regarding the clinical efficacy of granulocyte transfusions for the treatment or prophylaxis of life-threatening infections in neutropenic patients have been attributed to insufficient number of transfused neutrophils. Since the introduction of granulocyte colony-stimulating factor (G-CSF) to the granulocyte mobilization regimen in the 1990s, the number of transfused cells significantly increased, which directly translated to a significant increase in absolute neutrophil counts in the transfused patients.

For therapeutic granulocyte transfusions, neither of the two randomized controlled studies in the G-CSF era could demonstrate a clear clinical benefit. However, a number of small studies or case series have suggested its clinical efficacy, including one that demonstrated the clinical response against drug-resistant invasive fusariosis. For prophylactic granulocyte transfusions, there have been scarce reports in the G-CSF era. A pulmonary reaction is the most significant adverse event after granulocyte transfusions, although its reported frequency varies among studies.

Despite the expectation that the increased number of transfused neutrophils enables the clear demonstration of the clinical benefit, the role of therapeutic granulocyte transfusions remains controversial. Future directions may include: identifying the patient population who would benefit most from granulocyte transfusions; minimizing the risk of adverse events by identifying the risk factors and the prevention methods; and finding a way to prove the clinical benefit of granulocyte transfusions in therapeutic and prophylactic settings.