Dr. Marco Mielcarek is the medical director of the Adult Blood and Marrow Transplant Program at Fred Hutchinson Cancer Center. His research focuses on graft-vs.-host disease, or GVHD, a potentially life-threatening complication in which newly transplanted cells attack the patient’s body. Dr. Mielcarek and his research colleagues are testing in clinical trials how to better prevent GVHD and how to effectively treat it without causing unwanted toxicity. He and his colleagues have shown that carefully timed infusions of high doses of cyclophosphamide, a common chemotherapy drug, can safely and effectively prevent GVHD after growth factor-mobilized blood stem transplantation.