Monitoring chelation therapy to achieve optimal outcome in the treatment of thalassaemia

Abstract

Effective management of iron overload in thalassaemia requires monitoring both for iron toxicity and the effects of excessive chelation. Careful monitoring together with adherence to established regimens using desferrioxamine (DFO) results in a 78% survival rate at 40 years of age at UCLH, with steadily improving survival as progressive cohorts receive chelation earlier in life. By contrast, survival is considerably below this in non-specialist centres. The prognostic significance of the measures being used in monitoring should be known so that decisions about chelation management are evidence-based. Serum ferritin measurement, although easy to perform frequently, is subject to variability and falsely high or falsely low values in relation to body iron are frequently obtained. However, there is evidence that persistently high ferritin values above 2500 microg/l have poor prognostic significance in patients treated with DFO. Liver iron predicts total body iron in a more predictable way than serum ferritin in thalassaemia. Liver iron concentrations of 15 mg/g dry weight appear to predict those patients who develop heart failure in subjects treated with DFO. The prognostic significance of this measurement or indeed other measurements of iron overload in patients treated with other chelation regimens is not known. Recent advances with MRI imaging have aroused interest in its use for monitoring patients with thalassaemia. A recent publication suggests a relationship between left ventricular ejection fraction and cardiac T2*, the value of which shortens with increasing iron concentrations in the liver and hence by inference in the heart. The prognostic value of this technique has not yet been demonstrated in prospective studies and hence changes in therapy based on this measurement alone should be considered with caution at this time. The value of monitoring to decrease morbidity from iron overload is also discussed, particularly with reference to the estimation of iron deposition in the pituitary.