Bendamustine With or Without Cyclophosphamide in Preventing GVHD in Patients Undergoing Stem Cell Transplant

This phase I/II trial studies the side effects and best dose of bendamustine when given with or without cyclophosphamide in preventing graft versus host disease (GVHD) in patients undergoing stem cell transplant. Drugs used in chemotherapy, such as bendamustine and cyclophosphamide, work in different ways to stop the growth of cancer cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. Giving chemotherapy and total body irradiation before or after a stem cell transplant helps kills cancer cells that are in the body and helps make room in the patient's bone marrow for new blood-forming cells (stem cells) to grow. Sometimes, the transplanted cells from a donor can attack the body's normal cells called GVHD. Giving tacrolimus, mycophenolate mofetil, and filgrastim after the transplant may stop this from happening.