This is an investigational study. Ibandronate is commercially available and FDA approved for use in the prevention and treatment of bone loss in women who have been through menopause. However, its use in slowing the rate of bone loss in patients who have had a bone marrow transplant is considered experimental. For this purpose, the M. D. Anderson Institutional Review Board (IRB) has authorized the use of ibandronate for research only. The IRB is a committee made up of doctors, researchers, and members of the community. The IRB is responsible for protecting the participants involved in research studies and making sure all research is done in a safe and ethical manner.