Platelet Transfusions in Hematopoietic Stem Cell Transplantation (The PATH III Trial)

In Canada, over 1,500 autologous hematopoietic stem cell transplantations (ASCT) are performed annually for hematologic malignancies. It is currently standard practice to provide a prophylactic transfusion of platelets to prevent bleeding when the daily measured platelet count is less than 10 x 109/L. A patient may require up to six adult platelet doses during the post-transplant period. However, the true benefit of prophylactic platelet transfusions in the ASCT setting is unclear and has been called into question by several recent studies.

Prophylactic platelet transfusions may not only be unnecessary, they may be detrimental to the patient. Among blood products, platelet transfusions are associated with the highest risk of both infectious and non-infectious complications: this would include bacterial infections and allergic /febrile reactions. Moreover, the potential overuse of platelet products places a significant burden on a scarce health care resource that is provided through volunteer donations.

An alternative strategy to prevent bleeding and reduce the need for platelet transfusions involves administering Tranexamic Acid, an antifibrinolytic agent to stabilize blood clots and reduce bleeding. Tranexamic Acid is safe and effective in many clinical scenarios, and may be a reasonable alternative for prophylactic platelet transfusions. In the setting of ASCT, Tranexamic Acid may reduce bleeding and further enhance a strategy of therapeutic platelet transfusions where platelets are administered only in the event of active bleeding symptoms.

The effect of prophylactic platelet transfusions and Tranexamic Acid on clinical, quality of life and economic outcomes in patients receiving ASCT is unknown. The primary aim of this research program is to perform a randomized controlled trial to determine whether a strategy of prophylactic Tranexamic Acid (with therapeutic platelet transfusions) is safe and effective compared to prophylactic platelet transfusions in patients undergoing ASCT.

A pilot trial demonstrated feasibility by successfully recruiting 100 patients and these patients will be rolled over into the phase III study. The treatment assignment and bleeding outcomes for these patients remain blinded.

Inclusion criteria

• Adults 18 years or older undergoing ASCT for a hematologic malignancy
• Patients providing written informed consent prior to starting transplantation

Exclusion criteria

• A previous WHO grade 2, 3 or 4 bleeding event within the past year
• A previous or current unprovoked thrombotic event defined as a pulmonary embolism, deep vein thrombosis, cerebral thrombosis
• A current provoked thrombotic event (e.g. catheter-related thrombosis) within last month and/or still requiring anticoagulant treatment.
• A requirement for therapeutic anticoagulant or anti-platelet drugs during ASCT
• Active angina (chest pain of presumed cardiac origin either at rest or with activity)
• Current or previous (within 2 weeks) urinary tract bleeding
• An inherited hemostatic or thrombotic disorder
• Coagulopathy defined as a prothrombin time '/International Normalization Ratio (INR) or activated partial thromboplastin time more than 1.5 times the upper limit of normal or fibrinogen less than 2 g/L
• Previously documented history of refractoriness to platelet transfusion secondary to HLA antibodies (Refractoriness is defined as 2 consecutive ABO matched platelet transfusions with platelet increment of < 7.5 and the presence of anti-HLA antibodies)
• Significant renal impairment (creatinine more than 1.5 times the upper limit of normal or a eGFR less than 0.5 mL/min/1.78m2)
• Pregnant or breast-feeding
• Unwilling or unable to provide informed consent
• Participant has acquired disturbances to his/her colour vision (does not apply to congenital colour blindness)
• Participant has known sensitivity or allergy to Tranexamic Acid or any of its ingredients