Thalassemia Clinical Research Network (TCRN)

BACKGROUND:

Cooley's anemia (beta-thalassemia major, hereafter referred to as thalassemia) is a severe, inherited blood disorder characterized by a quantitative defect in the synthesis of the beta chain of hemoglobin caused by any 1 of more than 100 known mutations in and around the beta globin gene cluster. The disease is characterized by severe anemia beginning in the first 6 to 12 months of life. If untreated, the life expectancy is less than 5 years of age. Chronic red blood cell transfusions to maintain hemoglobin levels between 9 and 11 gm/dl ("hypertransfusion") alleviate the anemia and partially suppress erythropoiesis. The regular administration of red blood cells also improves growth, delays or prevents enlargement of the liver and spleen, and prevents the development of bone abnormalities that cause fractures as well as disfiguring changes known as Cooley's facies. Transfusions carry risks of alloimmunization, iron overload, and blood-transmitted infections. In the absence of effective iron chelation therapy, iron overload leads to numerous complications, including delayed or absent sexual development, diabetes mellitus, cirrhosis, cardiac arrhythmias, and congestive heart failure. Nonchelated or poorly chelated patients usually die of heart disease by 20 to 30 years of age.

The addition of chelation therapy with deferoxamine (DFO) to the treatment of Cooley's anemia has dramatically improved the outcome for affected patients. With regular chelation therapy, the accumulation of excessive iron can be prevented. Studies have demonstrated that well-chelated patients have normal or only modest increases in liver iron, improved growth, sexual development, and most importantly, a markedly reduced chance of developing iron-induced heart disease.

In the past few years, several new approaches to the treatment of thalassemia have included marrow or stem cell transplantation; the use of young red blood cells ("neocytes") for transfusion; maintenance of a higher pretransfusion hemoglobin level; new iron chelators; and the use of drugs such as hydroxyurea, erythropoietin, and butyrate compounds.

It is recognized that even with a clinical network, the number of patients with Cooley's anemia who can be enrolled in a research protocol is likely to be small. Therefore, although a randomized clinical trial may be the preferred way of assessing the clinical benefits of a new therapy, it may not be feasible in some instances, even using biomarkers or other surrogate outcome measures. Depending upon the specific questions being addressed, other study designs might be appropriate. These might include pre- and post-treatment assessment or historical control studies. In all cases, the proposed design, including sample size, would be evaluated by the Protocol Review Committee.