Suboptimal Long Term Engraftment Does Not Negatively Impact Overall Survival after Autologous Peripheral Blood Stem Cell Transplant

The importance of optimal long term engraftment after autologous stem cell transplantation is uncertain. We conducted a retrospective analysis of long term engraftment in patients who underwent autologous peripheral blood stem cell transplant for non-Hodgkin lymphoma, Hodgkin lymphoma or multiple myeloma.  Patients who relapsed or died prior to assessment of long term engraftment at 1 year were excluded. Optimal engraftment was defined by NCI CTCAE grade 1 criteria for cytopenias (ANC ≥ 1500/ml, platelets ≥ 75000/ml, hemoglobin ≥ 10g/dL).  225 patients were identified with engraftment data at 1 year (92 NHL, 62 HL, 71 MM).  The median follow-up was 5.0 years for all patients (5.5 for living patients).

88% of patients achieved optimal engraftment at 1 year.  The median cell dose was 4.7 x10^6 CD34+ cells/kg, and our institutional minimum cell dose is 2 x10^6 CD34+ cells/ kg.  CD34 cell dose ≥ 3 x10^6 CD34+ cells/kg and age < 60 were predictive for optimal long term engraftment.  Disease type, gender, number of prior therapies and prior radiation therapy were not predictive of achieving long term engraftment.  By landmark analysis at 1 year, optimal engraftment was not predictive for progression free survival or overall survival in all patients, although there was a trend for worse outcome with poor engraftment in HL and NHL.  

Incomplete long term engraftment after autologous transplant is relatively rare with the most important predictors identified as CD34 cell dose and age.  For those patients who survive one year, PFS and OS are not diminished afterward.