Most chemotherapeutic agents are myelosuppressive, causing neutropenia and thrombocytopenia, especially when used in moderate to high doses. The advent of platelet transfusions in the mid-1960s led to a marked decrease in bleeding complications from chemotherapy induced thrombocytopenia. Originally, platelets were collected from single units of whole blood donated to blood banks and pooled in units of 6 to 8 for transfusion purposes. However, in order to reduce the risks of alloimmunization and occult disease, transmission platelets were subsequently collected from single volunteer or family member donors. Collection of platelets from a single donor is accomplished by an apheresis technique where platelets are extracted and red blood cells and plasma are returned to the donor. At the present time, over 60% of all platelets administered by blood banks in the U.S. are from single donors. In some areas, this percentage is even higher. Single donors can also be selected to be “compatible” with the recipient in many instances where immunization is present. Immunization occurs from transfusions of red blood cells or platelets, but many women will be immunized by pregnancy and do not respond to fresh platelets from allogeneic donors when administered for the first time. The ability to cryopreserve platelets has been available for a decade or more but the methodology requires a cryopreservative, dimethylsulfoxide (DMSO), which can be toxic to patients and must be removed before administration and patients with normal platelet levels yield inadequate numbers of platelets.

Researchers from MD Anderson Medical Center have reported that two of the main obstacles to the practical use of autologous frozen platelets have been surmounted. They report in the June 20 issue of The Lancet that autologous platelet transfusions are now practical. They used a newly developed storage solution called ThromboSol, which allowed the reduction of the concentration of DMSO from 6% to 2%, with retention of good viability on thawing. They also report that the administration of two doses of thrombopoietin increased platelet counts two to four-fold, making it possible to collect large quantities of platelets with 2-3 apheresis procedures.

They compared cryopreserved autologous platelet transfusions to fresh allogeneic platelet transfusions in women with gynecologic malignancies receiving 6 cycles of carboplatin based chemotherapy. Women in this study were randomly allocated to receive either cryopreserved autologous or fresh allogeneic platelets when they first developed a platelet count below 15,000. After each subsequent course of therapy, patients received the alternate source of platelets for comparison. There was no significant difference in platelet increments between the 19 paired transfusions of cryopreserved autologous platelets and fresh allogeneic platelets. Fourteen of the 19 patients had a good response to their first transfusion of allogeneic platelets, while all patients had a good response to their first transfusion of autologous platelets. There was no significant decrease in platelet increments after multiple treatment cycles following 63 autologous platelet transfusions. No transfusion reactions or any serious adverse event was recorded during autologous platelet transfusions. Following 50 allogeneic platelet transfusions, there were reactions in 5 patients. Six patients became refractory to fresh allogeneic platelet transfusions during the study.

Comments: This study clearly shows the potential benefit of cryopreserved autologous platelets. When this is performed in a timely manner, before damage to the bone marrow, this should allow physicians to avoid the high costs of supporting platelet refractory patients and would also avoid transmission of infectious diseases. The authors also speculate that this technology would allow for the storage of specific HLA types for use in refractory patients.

Reference: Vadhan-Raj S, John J Kavanagh JJ, Ralph S Freedman RS, et al. Safety and efficacy of transfusions of autologous cryopreserved platelets derived from recombinant human thrombopoietin to support chemotherapy-associated severe thrombocytopenia: a randomised cross-over study. The Lancet. 2002:359:2145-2152.