Thalassemia Syndromes |
1 Department of Haematology, Barts and the London School of Medicine and Dentistry, London UK
2 Department of Biostatistics, City University, London, UK
3 Thalassaemia Centre, Archbishop Makarios III Hospital, Nicosia, Cyprus
4 Thalassaemia Centre, Limassol General Hospital, Limassol, Cyprus
5 Thalassaemia Centre, Archbishop Makarios III Hospital, Larnaca, Cyprus
6 Thalassaemia Centre, Paphos General Hospital, Paphos, Cyprus
7 Thalassaemia International Federation, Nicosia, Cyprus
Correspondence: Paul Telfer, Department of Haematology, Barts and the London School of Medicine, 4th Floor, New Pathology and Pharmacy Block, 80 Newark Street, London, UK. E-mail: paul.telfer{at}bartsandthelondon.nhs.uk
Key words: thalassaemia, chelation, survival, combination, deferiprone, desferrioxamine.
Life expectancy in thalassemia major (TM) is reduced, mainly as a result of deaths from transfusion iron-overload and cardiac dysfunction. Early deaths are preventable by effective long-term iron chelation therapy, but 50% are unable to adhere adequately to standard treatment consisting of sub-cutaneous desferrioxamine (DFO) infusions administered at least five times per week.1,2 In a previous report on a cohort of TM patients treated in Cyprus, we noted a significantly lower incidence of fatal events co-inciding with follow-up and treatment after 1999,3 an observation also made in the UK.4 The oral chelating agent deferiprone (DFP) was licensed in the European Union in 1999. Since effectiveness of DFP as monotherapy was thought to be insufficient, and there had been reports of more efficient chelation when DFP was used in combination with DFO,5 a protocol of combination chelation therapy (CCT) was introduced in Cyprus to optimize the benefit from DFP. In the previous study, we suggested that use of CCT was the explanation for the decrease in mortality, but could not show this statistically due to insufficient data. With a further two years of follow-up, we have readdressed this question.
Indications for CCT were: moderate or high iron stores (ferritin <1500 µg/L), cardiac dysfunction (symptomatically or on echocardiography) or decreased myocardial T2* (<20 milliseconds). The protocol for CCT was similar to that described by Origa et al.:6 DFP 75–100 mg/kg per day seven days per week, and DFO 30–50 mg/kg over 12–24 hours 2–5 infusions per week depending on ferritin levels. DFO was generally stopped if ferritin was consistently <500 µg/L, but DFP continued.
The patient cohorts and methods of follow-up were described in the original publication.3 The cohort born after 1973 has undergone an additional analysis as a birth cohort (these patients were prospectively registered at diagnosis and consist of all new diagnoses in Cyprus). Cox Proportional Hazards was used to assess factors impacting on survival with CCT modelled using time of starting as a time-dependent covariate. We exclude those treated for less than six months.
Demographic data are shown in Table 1. The full cohort includes 5 more than in the previous publication: these had been erroneously omitted. Sixty-five patients died between 1/1/80 and 31/12/06. Thirty-two (49% of deaths) were from cardiac causes. Other causes of death were: infection 9 (14%), accident 6 (9%), other 6 (9%), not known 5 (8%), malignancy 4 (6%), liver disease 3 (5%). Within the Birth Cohort, 18 (6%) patients died, 7 from cardiac causes.
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Table 1. Demographic data for Cyprus patients.
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Results of multivariable analysis are shown in Table 2. For CCT, the hazard ratio of 0.14 equates to 7.4-fold improved survival for each year on therapy. In the birth cohort, CCT was the only independent factor associated with survival. For cardiac deaths, the effect of CTT could not be calculated since there were no events in those initiated on therapy. Making an arbitrary assumption that the patient with the median duration of CCT had in fact died of a cardiac cause, CCT is associated with a 4-fold increased chance of survival from cardiac death.
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Table 2. Hazard ratios for prediction of survival in multivariate analysis.
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This study provides good evidence that CCT is effective in controlling body iron stores in moderately to heavily iron loaded patients and prevents iron overload related deaths. It is not clear whether equal benefits would be obtained with DFP monotherapy, as shown in another study,10 or with the new oral iron chelating drug deferasirox, where the efficacy in terms of survival has not yet been established. We observed a high rate of discontinuations and of severe but manageable adverse events with CCT, highlighting the need for supervision from a specialist center. Management of the risk of agranulocytosis requires weekly full blood counts, and periodically reminding patients about this potential risk.
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C. Borgna-Pignatti The life of patients with thalassemia major Haematologica, March 1, 2010; 95(3): 345 - 348. [Abstract] [Full Text] [PDF] |
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