We conducted a prospective pilot study of permissible dose reduction with PT/Cy.
Incidence of grade II–IV acute GVHD tended to depend on PT/Cy dose.
Cumulative incidence of chronic GVHD was low irrespective of PT/Cy dose.
Infused CD34+ cell counts significantly correlated with grade of acute GVHD.
PT/Cy 25 mg/kg × 2 yielded better outcomes compared with PT/Cy 25 mg/kg.