Influence of Timing PTCy in AlloSCT

Plain-language summary

Cyclophosphamide, administered after the infusion of haematopoietic progenitor cells, is used to prevent graft-versus-recipient disease (GVHD) in patients undergoing allogeneic haematopoietic stem cell transplantation (allogeneic HSCT) and has been shown to reduce the incidence of GVHD. Cyclophosphamide can cause haemorrhagic cystitis as a result of the direct toxicity of its metabolite acrolein to the bladder mucosa or urothelium upon accumulation in the urine. Hyperhydration and the administration of mesna, which forms a non-urotoxic compound with acrolein, are among the most commonly used strategies to prevent this. The administration of cyclophosphamide in the morning is also recommended. The protocol for post-transplant cyclophosphamide states that it should be started at least 72 hours (days +3 and +4) after haematopoietic progenitor infusion, but this interval can be extended to 84 hours (day +3.5). After reviewing the recommendations to reduce the risk of haemorrhagic cystitis, it was recommended to delay the infusion of cyclophosphamide to the early morning of days +4 and +5, although in reality, taking into account the hours since the infusion of haematopoietic progenitors, it would be days +3.5 and +4.5 instead of days +3 and +4 in the afternoon/evening. This change will mean a delay of 12 hours in the start of cyclophosphamide, so the investigators will refer to day +3.5 from the infusion of the haematopoietic precursors.

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