BMTs done in the late 1950s to the late 1960s were often disappointing. Most patients who had transplants were terminally ill and often died soon after the transplant. Many patients receiving BMT were given bone marrow that was not typed correctly. Some patients died of graft versus host disease (GVHD), in which the transplanted tissue attacks the person it was supposed to cure, or succumbed to infections that took advantage of the patient's weakened immune system.
In the early 1970s there were dramatic improvements in the survival rates of patients undergoing the procedure. This was due to HLA typing, which was established around that time. BMTs were also more successful because leukemia patients received transplants while in remission and because supportive care had improved. The results of BMTs continued to improve through the 1970s and 1980s as new antibacterial, antifungal, and antiviral agents were developed. At the same time, medications called growth factors were developed, which increased the patients neutrophil counts so they had fewer infections. Today, the cure rate for acute leukemia patients receiving BMT is about 50-70%; for chronic myelogenous leukemia, it's about 70-80%; and for aplastic anemia, it's 60-80%. In the relatively short time of about four decades, the bone marrow transplant procedure has become a successful form of treatment for a number of illnesses. Many patients who would die otherwise can be saved through the BMT. The use of blood as a stem cell source redefined this procedure to stem cell transplant (SCT), but the basic idea is the same: stem cells from a healthy donor are used to replace diseased tissue.
