What factors can predict the success of stem cell transplantation?

This study evaluated the risk factors associated with delayed engraftment (DE) in patients who had stem cell transplantation (SCT). The authors found that patients receiving blood transfusions, those with low platelet levels, and those given low numbers of stem cells during SCT were more likely to experience DE.

Autologous SCT is a treatment used for different cancers involving blood cells. Healthy stem cells (immature blood cells) are collected from the patient's blood or bone marrow. Then, the patient is given high-dose chemotherapy to get rid of any remaining cancer cells. After treatment, the stem cells are given back to the patient (transplantation). 

After the transplant, the stem cells make their way to the bone marrow and start to make new blood cells. This process is called engraftment. Engraftment usually happens over 10 to 20 days, but sometimes it can happen slowly. This is called delayed engraftment (DE). Which factors increase the risk of DE in patients with lymphoma or leukemia are unclear.

This study involved 1162 patients with lymphoma or leukemia who underwent autologous SCT. 15 patients had acute myeloid leukemia (AML). Patients were followed up at 30 days, 3 months, 6 months, and 1 year after SCT. 

After 30 days, 224 patients had DE. Out of the 15 patients with AML, 73.9% had DE. 181 patients (80.8%) had DE because of low platelet counts (cells involved in blood clotting). After 3 months, 111 patients continued to have DE. Of these, 102 patients (91.9%) had DE because of low platelet counts. After 6 months, this rate was 24.1% (54 patients). At 1 year, this rate was 7.6% (17 patients). 

Having low platelet levels before SCT was significantly associated with DE. Significantly more patients with low platelet levels had DE after 3 months compared to patients who had normal levels (61.5% vs. 35.8%). Patients with low platelet levels had a 3-fold higher risk of developing DE. 

Receiving a lower dose of stem cells during SCT was also significantly associated with DE. 71.4% of patients who received low numbers of stem cells developed DE. 56.05% of patients who received higher numbers of stem cells developed DE. Patients who received less than 3 x 106 cells/kg were almost 6-fold higher risk of developing DE. 

Receiving a blood transfusion before SCT was also significantly associated with DE. 67.57% of patients who had a blood transfusion before the transplant developed DE compared to 47.22% who did not receive a transfusion. Patients who had blood transfusions before the transplant were 74.4% more likely to experience DE.

This study concluded that having low platelet levels, receiving blood transfusions, and receiving low numbers of stem cells during SCT can increase the risk of DE.

This study was retrospective, meaning it looked back in time to analyze data. This study followed patients over 20 years, during which standards of care may have changed. More studies are needed to confirm these results.