Can stem cell transplantation be used to treat solid tumors yet?

Not likely.: It is most often done for patients with certain cancers of the blood or bone marrow, like multiple myeloma or leukemia. Graft-versus-host disease is a major complication. Others include veno-occlusive disease, mucositis, infections (sepsis), and oral cancer, so it is unlikely to be used for new things yet. It is reserved for life threatening conditions.

Not so many: High dose chemotherapy with hematopoietic stem cell transplantation has been shown to be effective for leukemia, lymphoma, multiple myeloma, and testicular cancer. It may be effective in other solid tumors, e.g. breast cancer, but has been shown to be better than less intensive therapies.