Prior stem cell transplantation (SCT): Prior HLA-matched (5-6/6 antigen or 8-10/10 allele) related or unrelated allogeneic SCT required. Must be at least 42 days post-transplant, have had recovery of transplant-associated toxicity to less than grade 2, and have post-transplant donor engraftment as defined by donor chimerism greater than 50 percent (peripheral blood), neutrophil recovery to an absolute neutrophil count (ANC) greater than 500/microl independent of myeloid growth factors, and platelet recovery to greater than 20,000/microL independent of transfusion.