Impact of graft cryopreservation on allogeneic hematopoietic stem cell transplant outcomes using post-transplant cyclophosphamide

This study aimed to compare outcomes of allogeneic hematopoietic stem cell transplant (alloHSCT) using cryopreserved (frozen) and fresh grafts in patients with blood cancers who received post-transplant cyclophosphamide (Cytoxan). This study concluded that cryopreservation (CP) does not affect the outcomes of HSCT in these patients.  

Allogeneic hematopoietic stem cell transplantation (alloHSCT) is a procedure in which a person receives blood-forming stem cells from a genetically similar, but not identical, donor. This is often a sister or brother but could be an unrelated donor. AlloHSCT is used after an initial treatment to replace healthy cells that may have been lost after chemotherapy or radiotherapy.  

Post-transplant cyclophosphamide (ptCY) is a treatment used to prevent graft-versus-host-disease (GVHD). GVHD is a side effect of HSCT where the transplanted cells attack the body of the patient. 

Due to the COVID-19 pandemic, many sites are now using cryopreservation (CP; freeze to preserve) to ensure grafts are available on the day of alloHSCT. However, the impact of CP on the outcome of alloHSCT using ptCY is unknown.    

This study involved 274 patients with a blood cancer such as leukemia or lymphoma. All patients had undergone alloHSCT with CP grafts and ptCY. These patients were compared to 1080 similar patients who underwent alloHSCT with fresh grafts (FG). 

The 1-year probability of overall survival (OS) was similar for the FG group (71.1%) and the CP group (70.3%). The 2-year probability of OS was also similar for the FG group (60.6%) and the CP group (58.7%).  

The rates of neutrophil (white blood cells involved in fighting infections) recovery, platelet (blood cells involved in clotting) recovery, severe short-term GVHD, and relapse/progression were similar for both groups. The rates of long-term GVHD (by 22%) and disease-free survival (DFS; by 19%) for the CP group were somewhat lower than the FG group. 

This study concluded that graft cryopreservation for patients undergoing alloHSCT with ptCY seems safe and similarly effective to fresh graft HSCT.

Most of the patients received peripheral blood CP grafts. Also, this study was based on medical records data. Therefore, data might have been incomplete. This might have affected the results.