Hematopoietic stem cell (HSC) transplantation is a common technique that may offer a cure to patients with hematologic cancers and disorders. The stem cells can be harvested from bone marrow, peripheral blood, or umbilical cord blood; and HSC transplantation can be autologous or allogeneic. When considering autologous HSC transplantation, which of the following factors is most likely to be a contraindication for this procedure?