Hematopoietic progenitor cell collection after autologous transplant for multiple myeloma: Low platelet count predicts for poor collection and sole use of resulting graft enhances risk of myelodysplasia

Collection of hematopoietic progenitor cells (HPC) after previous autologous hematopoietic progenitor cell transplant (aHCT) was studied in 221 patients with multiple myeloma (MM). With a total of 333 collections, the median number of CD34+ cells collected was 4.7 × 10 6 CD34+ cells/kg, and 74% of the patients collected ≥2.5 × 10 6 CD34+ cells/kg. Among 26 variables examined, the strongest predictor for poor collection was a platelet count <100 × 10 6/l before mobilization (P<0.001). A subsequent aHCT was performed in 154 of the 221 patients. Sole use of HPC procured after aHCT in 86 patients was associated with delayed platelet recovery (P<0.001) and linked to development of myelodysplastic syndrome (MDS)-associated cytogenetic abnormalities (MDS-CA; P=0.027, odds ratio (OR) 10.34) and a tendency towards clinical MDS/acute myeloid leukemia (AML; P=0.091, OR 3.57). However, treatment-related mortality (P=0.766) and time to absolute neutrophil count recovery ≥0.5 × 10 9/l (P=0.879) were similar to when a pre-aHCT graft was used. Indeed, adding HPC collected before any aHCT neutralized the risk of MDS-CA or MDS/AML. Therefore, we advise generous initial HPC collection to broaden the salvage armamentarium for patients with MM.