Reduction of Hepatic Iron in Patients with Thalassemia Major According to Iron Chelation Regime Assessed by MRI T2*

Abstract

In 212 thalassemia major patients, repeated assessments for cardiac and hepatic iron (LIC) assessed by Magnetic Resonance Imaging (MRI – T2*) have been performed. The chelation regimes were either desferrioxamine (DFO), deferiprone (DFP), combination of DFO and DFP (Comb) or deferasirox (DFX). In general over the last few years, tailoring of chelation therapy has been principally guided by the cardiac iron loading. As many patients had been found to have excess cardiac iron, the majority (48%) had been placed on Comb. Patients were grouped according to the degree of siderosis. A T2* of <1.6ms was regarded as heavy LIC, between 1.6–4.0 moderate, 4.1–9.0 mild and > 9.1 acceptable. Taking into account that the change in T2* is not necessarily linear with respect to time and as the overall time of exposure to DFO, DFP and Comb regimes was significantly greater than that with DFX it was unjustified to perform comparative analysis using the total time period of the patients who were on any of the non DFX regimes. Therefore, to compare the efficacy of the four regimes on LIC, we performed an analysis using student T test to assess the rate of change only between the first and second MRI in patients with comparable LIC according to each chelation regime with adjustment for overall time of exposure (Table 1). Using the same data and applying linear regression analysis (Table 2) we compared the effect of DFO to the other three regimes in the annual rate of increasing hepatic T2*. Only Comb is effective at all levels of hepatic iron loading in reducing the iron content. DFX is effective in the mildly iron loaded patients and for the moderately iron loaded patients, its efficacy approaches statistical significance. DFP does not seem to significantly decrease LIC at any level of hepatic iron load however the numbers of patients in that group are very small. Interestingly DFO seems the least effective at all levels of hepatic iron loading and particularly in the heavy loaded patients. This factor may be related to poor compliance to its use as the patients who have reached such levels of iron load are more often those who are not compliant. In the comparison analysis to DFO, only Comb is significantly better and DFP and DFX are equivalent to it. In addition Comb is more effective than DFX and DFP in that over 12 months it would increase the T2* by 3.8ms (p <0.001) and 3.9ms (p 0.012) respectively. DFX and DFP are similar in efficacy in that they maintain the liver iron at the same levels (DFP vDFX 0.009ms p=0.95). In patients with hepatic T2* >9ms, 4 of 11 on DFO, 5 of 6 on DFX, 7 of 11 on DFP and 3 of 22 on Comb fell below 9. It is of note that DFO only maintains LIC and that a number of patients in the normal range increased LIC. Taking this data into account the DFX and DFP results are compatible with those seen both in the clinic and in trials. It is apparent however that combination therapy is the most effective regime for reducing hepatic iron significantly. As with cardiac iron loading, by knowing the degree of hepatic iron loading by the non-invasive T2* measurement and being able to manipulate patients chelation regimes, it seems possible to be able to have patients free of excess hepatic iron and potentially reduce other iron related morbidities as well.Table 1Annual estimated mean change in T2* according to severity of hepatic siderosisRegimeHeavyModerateMildΔT2*pΔT2**pΔT2*pDFO n= 42 tm*= 24.60.050.50.570.370.10.7DFP n= 11 tm= 23.80.560.250.880.313.50.19Comb n= 101 tm=21.71.170.00643.6<0.0015.9<0.001DFX n=58 tm=15.23.10.111.250.063.80.014*tm= mean time (in months) between MRI studiesTable 3Mean estimated difference in T2*Standard ErrorpDFP v. DFO−0.71.60.7Comb v DFO3.11.050.03DFX v DFO−0.71.20.5