Bortezomib Before Donor Stem Cell Transplant in Treating Patients With Multiple Myeloma

Rationale: Giving bortezomib and low doses of chemotherapy and total-body irradiation before a donor stem cell transplant or peripheral blood stem cell transplant helps stop the growth of cancer cells. It also stops the patient's immune system from rejecting the donor's stem cells. The donated stem cells may replace the patient's immune cells and help destroy any remaining cancer cells (graft-versus-tumor effect). Sometimes the transplanted cells from a donor can also make an immune response against the body's normal cells. Giving sirolimus and tacrolimus before and after transplant may stop this from happening. Purpose: This phase I/II trial is studying the side effects and best dose of bortezomib before donor stem cell transplant in treating patients with multiple myeloma.