An internationally known cancer expert and chairman of several Children's Oncology Group national study committees, Nachman was an authority in the medical management of childhood cancers--especially leukemia and lymphoma. He helped develop a treatment regimen known as "augmented post-induction therapy" for acute lymphoblastic leukemia (ALL) and led the clinical trial, published in 1998, that demonstrated a substantial improvement in survival for patients with ALL who had a slow response to initial therapy. These studies helped lead to the high cure rate for this disease today.