Comparison of Hematopoietic Reconstitution after Autologous Transplantation Using Stem Cells after Short- (<12 Months) and Longer-Term Cryostorage.

High-dose chemotherapy with autologous hemopoietic stem cell (HSC) transplantation is an important treatment option for patients with refractory or relapsed non-Hodgkin or Hodgkin lymphoma (NHL or HL). Although it is customary to collect the HSCs at the time the need is apparent, in theory collections carried out at an earlier stage of the disease - preferably when the patient is in remission - may have advantages in that 1) such HSCs will have been less exposed to damaging cytotoxic chemotherapy and 2) early collections may be less likely to be contaminated with malignant cells. However such "prophylactic" or "rainy day" harvests may need to be stored for extended periods before use, raising questions about their functional capacity. Although laboratory studies of the effects of long-term storage on the viability and proliferative capacity of cryopreserved HSCs have demonstrated that the cells remain functional, there have been few studies of clinical outcomes after their reinfusion. Because we have had a long-standing policy of carrying out "rainy day" harvests, we have had the opportunity to retrospectively compare rates of neutrophil and platelet engraftment, and 30-day transplant related mortality (TRM), of patients undergoing HSC transplantation after short-term (<1 year) and longer-term (range 1–9.3 years, median 2.2 years) cryostorage. Of the 133 NHL and HL patients transplanted at our hospital between 1985 and 2005, 98 were in the short-term and 35 in the longer-term group. TRM was 7/98 and 1/35 for the short- and longer-term groups, respectively (P=0.7); no deaths occurred in the 77 patients transplanted after 1998. Hematopoietic reconstitution was achieved in all 125 patients who survived 30 days. Neutrophil recovery (absolute neutrophil count >0.5 x 10⁹/L) was achieved by 12.2 ± 4.2 (SD) days and 14.2 ± 6.5 days post-reinfusion for the short- and longer-term groups respectively (P=0.14). Platelet support was required for a mean 6.6 ± 9.5 and 7.5 ± 7.1 days, respectively (P=0.7). These clinical results demonstrate that HSCs after long-term cryostorage retain engraftment potential similar to that of HSCs stored for lesser periods and that such cells are safe and efficacious for autologous transplantation.