TPMT and acute lymphoblastic leukemia: We also did not alter 6MP dose based on TPMT status, white blood cell (WBC) counts or RBC TGN levels as is recommended in the treatment of paediatric ALL.44 In fact, following the pre-planned safety review in the first 12 patients, a dose reduction from 75 to 55 mg/m2 was required due to the high rates of myelosuppression and dose reductions required.